Block acknowledgment for multi-user transmissions in wlan systems

ABSTRACT

In wireless communications for multi-users, a station may generate a first frame and transmit the first frame to an access point. The first frame may include media access control protocol data units (MPDUs). Each MPDU is associated with a traffic identifier (TID). In one aspect, a TID of one of the MPDUs is different from a TID of another one of the MPDUs. In response to receiving the first frame, the access point may generate a second frame based on the first frame. The second frame may include an indication that all of the MPDUs having TIDs are received. The access point may transmit the second frame to the station. Other methods, apparatus, and computer-readable media are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 15/237,566, entitled “BLOCK ACKNOWLEDGMENT FORMULTI-USER TRANSMISSIONS IN WLAN SYSTEMS,” filed on Aug. 15, 2016, whichclaims the benefit of priority under 35 U.S.C. § 119 from U.S.Provisional Application No. 62/205,585, entitled “SUB-CHANNEL ASSIGNMENTMECHANISM FOR UPLINK MULTI-USER TRANSMISSION,” filed Aug. 14, 2015; U.S.Provisional Application No. 62/205,589, entitled “TRIGGER FRAME INA-MPDU,” filed Aug. 14, 2015; U.S. Provisional Application No.62/237,479, entitled “MULTI-STA BLOCK ACK OPERATION,” filed Oct. 5,2015; and U.S. Provisional Application No. 62/271,157, entitled “A-MPDUCONTENTS IN RESPONSE FRAME OF TRIGGER FRAME,” filed Dec. 22, 2015, theentirety of each of which is incorporated herein by reference.

TECHNICAL FIELD

The present description relates in general to wireless communicationsystems and methods, and more particularly to, for example, withoutlimitation, block acknowledgement for multi-user transmissions inwireless local area network (WLAN) systems.

BACKGROUND

Wireless local area network (WLAN) devices are deployed in diverseenvironments. These environments are generally characterized by theexistence of access points and non-access point stations. Increasedinterference from neighboring devices gives rise to performancedegradation. Additionally, WLAN devices are increasingly required tosupport a variety of applications such as video, cloud access, andoffloading. In particular, video traffic is expected to be the dominanttype of traffic in many high efficiency WLAN deployments. With thereal-time requirements of some of these applications, WLAN users demandimproved performance in delivering their applications, includingimproved power consumption for battery-operated devices.

The description provided in the background section should not be assumedto be prior art merely because it is mentioned in or associated with thebackground section. The background section may include information thatdescribes one or more aspects of the subject technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processor in a wireless communication device.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processor in a wireless communication device.

FIG. 4 illustrates an example of a timing diagram of interframe space(IFS) relationships.

FIG. 5 illustrates an example of a timing diagram of a carrier sensemultiple access/collision avoidance (CSMA/CA) based frame transmissionprocedure for avoiding collision between frames in a channel.

FIG. 6 illustrates an example of a high efficiency (HE) frame.

FIGS. 7-19 illustrate examples of an HE physical layer convergenceprocedure (PLCP) protocol data unit (PPDU).

FIGS. 20 and 21 illustrate examples in which multiple stationssimultaneously transmit uplink data frames to an access point.

FIGS. 22 and 23 illustrate examples of a frame exchange sequence usedfor uplink multi-user multiple-input-multiple-output (MU-MIMO)transmission.

FIG. 24 illustrates an example of a frame exchange sequence between anaccess point and multiple stations.

FIG. 25 illustrates an example of a recovery procedure of an uplinkMU-MIMO Poll procedure.

FIG. 26 illustrates an example of a Membership Status Array fieldformat.

FIG. 27 illustrates an example of a User Position Array field format.

FIGS. 28 and 29 illustrate examples of a frame exchange sequence betweenan access point and multiple stations.

FIG. 30 illustrates an example of an HE acknowledgement (ACK) frame.

FIG. 31 illustrates an example of a channel list parameter for a 40 MHz,80 MHz, and 160 MHz channel width.

FIGS. 32, 33, and 34 illustrate examples of a frame exchange sequencebetween an access point and multiple stations.

FIG. 35 illustrates an example of a block acknowledgement (Block ACK orBA) frame.

FIGS. 36-41 illustrate examples of an exchange of frames between anaccess point and multiple stations.

FIG. 42 illustrates an example of a Multi-User Block ACK Request(MU-BAR) frame.

FIG. 43 illustrates an example of a frame having sub-channel assignmentinformation.

FIG. 44 illustrates an example of a structure of a resource unit (RU)distribution in an orthogonal frequency division multiple access (OFDMA)transmission.

FIG. 45 illustrates an example of a general framework of a nestedstructure of an RU Sub-Channel sub-field.

FIG. 46A illustrates an example of a Common Sub-Channel Assignment Infofield.

FIGS. 46B and 46C illustrate examples of a Per-User Sub-ChannelAssignment Info field.

FIG. 47A illustrates an example of a Common Sub-Channel Assignment Infofield.

FIG. 47B illustrates an example of a Per-User Sub-Channel AssignmentInfo field.

FIG. 48 illustrates an example of a high throughput (HT) Control field.

FIG. 49 illustrates an example of an aggregated media access controlprotocol data unit (A-MPDU) format.

FIGS. 50 and 51 illustrate examples of a frame exchange sequence betweenan access point and multiple stations.

FIG. 52 illustrates an example of a Block ACK frame.

FIG. 53 illustrates an example of a frame exchange sequence between anaccess point and multiple stations.

FIG. 54 illustrates an example of a Block ACK frame.

FIG. 55 illustrates an example of a frame exchange sequence between anaccess point and multiple stations.

FIG. 56 illustrates an example of a Block ACK frame.

FIG. 57 illustrates an example of a frame exchange sequence between anaccess point and multiple stations.

FIGS. 58A, 58B, 58C, 58D, and 58E illustrate flow charts of examples ofmethods for facilitating wireless communication for uplink transmission.

In one or more implementations, not all of the depicted components ineach figure may be required, and one or more implementations may includeadditional components not shown in a figure. Variations in thearrangement and type of the components may be made without departingfrom the scope of the subject disclosure. Additional components,different components, or fewer components may be utilized within thescope of the subject disclosure.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious implementations and is not intended to represent the onlyimplementations in which the subject technology may be practiced. Asthose skilled in the art would realize, the described implementationsmay be modified in various different ways, all without departing fromthe scope of the present disclosure. Accordingly, the drawings anddescription are to be regarded as illustrative in nature and notrestrictive.

The Institute of Electrical and Electronics Engineers (IEEE) 802.11,Task Group ax, provides a new generation of wireless local area network(WLAN). In an aspect, IEEE 802.11ax may be referred to as HighEfficiency (HE) WLAN (HEW) or simply HE. IEEE 802.11ax provides a HighEfficiency WLAN (HEW) PPDU format. In some aspects, the HEW PPDU formatsmay support Multi-User (MU) Multiple-Input and Multiple-Output (MIMO)technology and/or Orthogonal Frequency Division Multiple Access (OFDMA)technology. HEW may operate in 2.4 GHz and 5 GHz bands with a channelbandwidth of 20 MHz or higher. For instance, the channel bandwidth maybe 20 MHz, 40 MHz, 80 MHz, 80+80 MHz, or 160 MHz (denoted as20/40/80/80+80/160 MHz).

In one or more implementations, in OFDMA, an access point may allocatedifferent portions of a channel bandwidth to different stations. In oneaspect, a portion of a channel bandwidth is allocated to a station. Inone aspect, a portion of a channel bandwidth may be a resource unit (RU)or a resource allocation block. In another aspect, a portion of achannel bandwidth may be one or more resource units. In yet anotheraspect, a portion of a channel bandwidth may be one or more blocks of achannel bandwidth. Each resource unit includes multiple tones. In anaspect, a resource unit may be referred to as a block, subband, band,frequency subband, frequency band, or variant thereof (e.g., frequencyblock). A tone may be referred to as subcarrier. Each tone may beassociated with or otherwise identified by a tone index or a subcarrierindex. A tone index may be referred to as a subcarrier index.

In one or more aspects, the resource units that may be allocated for achannel bandwidth may be provided by an OFDMA numerology. In an aspect,the OFDMA numerology may be referred to as an OFDMA structure or anumerology. The numerology provides different manners by which toallocate resources for a channel bandwidth (e.g., 20 MHz, 40 MHz, 80MHz, 80+80 MHz, or 160 MHz channel bandwidth) into individual resourceunits. In other words, the numerology provides potential resources forOFDMA for stations that support the IEEE 802.11ax specification.

In one or more aspects, a sub-channel assignment mechanism is disclosedfor uplink (UL) multi-user (MU) transmission. The mechanism may provide,for example, how to signal a frequency of a resource unit assigned for aUL MU transmission. In one or more implementations, an aggregated mediaaccess control protocol data unit (A-MPDU) format may include a framehaving sub-channel assignment information. In an aspect, a trigger framemay be included in an A-MPDU. For instance, an HE single MPDU mayinclude a trigger frame for supporting a UL MU response.

In one or more implementations, when a UL MU responder has an authorityto select the contents of an A-MPDU carried in the UL MU response frame,UL MU scheduling at the access point (AP) may be affected by the A-MPDUcontents. For example, if a UL MU responder transmits a frame of DataEnabled Immediate Response context, the AP needs to assign one or moresub-channel(s) to the previous UL MU responder in order to reply withthe immediate response. Accordingly, the UL MU scheduling algorithmutilized on the AP side may be affected by the A-MPDU contents carriedin the UL MU response frame. In an aspect, A-MPDU contents may beincluded in a response frame to a trigger frame. In this regard, thepresent disclosure provides rules regarding whether a frame solicitingan immediate response can be included in the A-MPDU contents carried inthe UL MU response frame.

The present disclosure also describes a multi-user (or multi-station)block acknowledgement operation. For example, a Block AcknowledgementRequest (BAR) may be transmitted in a UL MU physical layer convergenceprocedure (PLCP) protocol data unit (PPDU) for explicitly requesting aBlock Acknowledgement (Block ACK or BA) frame with an explicitparameter, such as a starting sequence number.

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network 100. In the wireless communication network 100,such as a wireless local area network (WLAN), a basic service set (BSS)includes a plurality of wireless communication devices (e.g., WLANdevices). In one aspect, a BSS refers to a set of STAs that cancommunicate in synchronization, rather than a concept indicating aparticular area. In the example, the wireless communication network 100includes wireless communication devices 111-115, which may be referredto as stations (STAs).

Each of the wireless communication devices 111-115 may include a mediaaccess control (MAC) layer and a physical (PHY) layer according to anIEEE 802.11 standard. In the example, at least one wirelesscommunication device (e.g., device 111) is an access point (AP). An APmay be referred to as an AP STA, an AP device, or a central station. Theother wireless communication devices (e.g., devices 112-115) may benon-AP STAs. Alternatively, all of the wireless communication devices111-115 may be non-AP STAs in an Ad-hoc networking environment.

An AP STA and a non-AP STA may be collectively called STAs. However, forsimplicity of description, in some aspects, only a non-AP STA may bereferred to as a STA. An AP may be, for example, a centralizedcontroller, a base station (BS), a node-B, a base transceiver system(BTS), a site controller, a network adapter, a network interface card(NIC), a router, or the like. A non-AP STA (e.g., a client deviceoperable by a user) may be, for example, a device with wirelesscommunication capability, a terminal, a wireless transmit/receive unit(WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal,a mobile subscriber unit, a laptop, a non-mobile computing device (e.g.,a desktop computer with wireless communication capability) or the like.In one or more aspects, a non-AP STA may act as an AP (e.g., a wirelesshotspot).

In one aspect, an AP is a functional entity for providing access to adistribution system, by way of a wireless medium, for an associated STA.For example, an AP may provide access to the internet for one or moreSTAs that are wirelessly and communicatively connected to the AP. InFIG. 1, wireless communications between non-AP STAs are made by way ofan AP. However, when a direct link is established between non-AP STAs,the STAs can communicate directly with each other (without using an AP).

In one or more implementations, OFDMA-based 802.11 technologies areutilized, and for the sake of brevity, a STA refers to a non-AP highefficiency (HE) STA, and an AP refers to an HE AP. In one or moreaspects, a STA may act as an AP.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device. The wireless communication device 200 includes abaseband processor 210, a radio frequency (RF) transceiver 220, anantenna unit 230, a memory 240, an input interface unit 250, an outputinterface unit 260, and a bus 270, or subsets and variations thereof.The wireless communication device 200 can be, or can be a part of, anyof the wireless communication devices 111-115.

In the example, the baseband processor 210 performs baseband signalprocessing, and includes a medium access control (MAC) processor 211 anda PHY processor 215. The memory 240 may store software (such as MACsoftware) including at least some functions of the MAC layer. The memorymay further store an operating system and applications.

In the illustration, the MAC processor 211 includes a MAC softwareprocessing unit 212 and a MAC hardware processing unit 213. The MACsoftware processing unit 212 executes the MAC software to implement somefunctions of the MAC layer, and the MAC hardware processing unit 213 mayimplement remaining functions of the MAC layer as hardware (MAChardware). However, the MAC processor 211 may vary in functionalitydepending on implementation. The PHY processor 215 includes atransmitting (TX) signal processing unit 280 and a receiving (RX) signalprocessing unit 290. The term TX may refer to transmitting, transmit,transmitted, transmitter or the like. The term RX may refer toreceiving, receive, received, receiver or the like.

The PHY processor 215 interfaces to the MAC processor 211 through, amongothers, transmit vector (TXVECTOR) and receive vector (RXVECTOR)parameters. In one or more aspects, the MAC processor 211 generates andprovides TXVECTOR parameters to the PHY processor 215 to supplyper-packet transmit parameters. In one or more aspects, the PHYprocessor 215 generates and provides RXVECTOR parameters to the MACprocessor 211 to inform the MAC processor 211 of the received packetparameters.

In some aspects, the wireless communication device 200 includes aread-only memory (ROM) (not shown) or registers (not shown) that storeinstructions that are needed by one or more of the MAC processor 211,the PHY processor 215 and/or other components of the wirelesscommunication device 200.

In one or more implementations, the wireless communication device 200includes a permanent storage device (not shown) configured as aread-and-write memory device. The permanent storage device may be anon-volatile memory unit that stores instructions even when the wirelesscommunication device 200 is off. The ROM, registers and the permanentstorage device may be part of the baseband processor 210 or be a part ofthe memory 240. Each of the ROM, the permanent storage device, and thememory 240 may be an example of a memory or a computer-readable medium.A memory may be one or more memories.

The memory 240 may be a read-and-write memory, a read-only memory, avolatile memory, a non-volatile memory, or a combination of some or allof the foregoing. The memory 240 may store instructions that one or moreof the MAC processor 211, the PHY processor 215, and/or anothercomponent may need at runtime.

The RF transceiver 220 includes an RF transmitter 221 and an RF receiver222. The input interface unit 250 receives information from a user, andthe output interface unit 260 outputs information to the user. Theantenna unit 230 includes one or more antennas. When multi-inputmulti-output (MIMO) or multi-user MIMO (MU-MIMO) is used, the antennaunit 230 may include more than one antenna.

The bus 270 collectively represents all system, peripheral, and chipsetbuses that communicatively connect the numerous internal components ofthe wireless communication device 200. In one or more implementations,the bus 270 communicatively connects the baseband processor 210 with thememory 240. From the memory 240, the baseband processor 210 may retrieveinstructions to execute and data to process in order to execute theprocesses of the subject disclosure. The baseband processor 210 can be asingle processor, multiple processors, or a multi-core processor indifferent implementations. The baseband processor 210, the memory 240,the input interface unit 250, and the output interface unit 260 maycommunicate with each other via the bus 270.

The bus 270 also connects to the input interface unit 250 and the outputinterface unit 260. The input interface unit 250 enables a user tocommunicate information and select commands to the wirelesscommunication device 200. Input devices that may be used with the inputinterface unit 250 may include any acoustic, speech, visual, touch,tactile and/or sensory input device, e.g., a keyboard, a pointingdevice, a microphone, or a touchscreen. The output interface unit 260may enable, for example, the display or output of videos, images, audio,and data generated by the wireless communication device 200. Outputdevices that may be used with the output interface unit 260 may includeany visual, auditory, tactile, and/or sensory output device, e.g.,printers and display devices or any other device for outputtinginformation. One or more implementations may include devices thatfunction as both input and output devices, such as a touchscreen.

One or more implementations can be realized in part or in whole using acomputer-readable medium. In one aspect, a computer-readable mediumincludes one or more media. In one or more aspects, a computer-readablemedium is a tangible computer-readable medium, a computer-readablestorage medium, a non-transitory computer-readable medium, amachine-readable medium, a memory, or some combination of the foregoing(e.g., a tangible computer-readable storage medium, or a non-transitorymachine-readable storage medium). In one aspect, a computer is amachine. In one aspect, a computer-implemented method is amachine-implemented method.

A computer-readable medium may include storage integrated into aprocessor and/or storage external to a processor. A computer-readablemedium may be a volatile, non-volatile, solid state, optical, magnetic,and/or other suitable storage device, e.g., RAM, ROM, PROM, EPROM, aflash, registers, a hard disk, a removable memory, or a remote storagedevice.

In one aspect, a computer-readable medium comprises instructions storedtherein. In one aspect, a computer-readable medium is encoded withinstructions. In one aspect, instructions are executable by one or moreprocessors (e.g., 210, 211, 212, 213, 215, 280, 290) to perform one ormore operations or a method. Instructions may include, for example,programs, routines, subroutines, data, data structures, objects,sequences, commands, operations, modules, applications, and/orfunctions. Those skilled in the art would recognize how to implement theinstructions.

A processor (e.g., 210, 211, 212, 213, 215, 280, 290) may be coupled toone or more memories (e.g., one or more external memories such as thememory 240, one or more memories internal to the processor, one or moreregisters internal or external to the processor, or one or more remotememories outside of the device 200), for example, via one or more wiredand/or wireless connections. The coupling may be direct or indirect. Inone aspect, a processor includes one or more processors. A processor,including a processing circuitry capable of executing instructions, mayread, write, or access a computer-readable medium. A processor may be,for example, an application specific integrated circuit (ASIC), adigital signal processor (DSP), or a field programmable gate array(FPGA).

In one aspect, a processor (e.g., 210, 211, 212, 213, 215, 280, 290) isconfigured to cause one or more operations of the subject disclosure tooccur. In one aspect, a processor is configured to cause an apparatus(e.g., a wireless communication device 200) to perform operations or amethod of the subject disclosure. In one or more implementations, aprocessor configuration involves having a processor coupled to one ormore memories. A memory may be internal or external to the processor.Instructions may be in a form of software, hardware or a combinationthereof. Software instructions (including data) may be stored in amemory. Hardware instructions may be part of the hardware circuitrycomponents of a processor. When the instructions are executed orprocessed by one or more processors, (e.g., 210, 211, 212, 213, 215,280, 290), the one or more processors cause one or more operations ofthe subject disclosure to occur or cause an apparatus (e.g., a wirelesscommunication device 200) to perform operations or a method of thesubject disclosure.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processing unit 280 in a wireless communicationdevice. The transmitting signal processing unit 280 of the PHY processor215 includes an encoder 281, an interleaver 282, a mapper 283, aninverse Fourier transformer (IFT) 284, and a guard interval (GI)inserter 285.

The encoder 281 encodes input data. For example, the encoder 281 may bea forward error correction (FEC) encoder. The FEC encoder may include abinary convolutional code (BCC) encoder followed by a puncturing device,or may include a low-density parity-check (LDPC) encoder. Theinterleaver 282 interleaves the bits of each stream output from theencoder 281 to change the order of bits. In one aspect, interleaving maybe applied only when BCC encoding is employed. The mapper 283 maps thesequence of bits output from the interleaver 282 into constellationpoints.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may use multiple instances of the interleaver 282 and multipleinstances of the mapper 283 corresponding to the number of spatialstreams (Nss). In the example, the transmitting signal processing unit280 may further include a stream parser for dividing outputs of the BCCencoders or the LDPC encoder into blocks that are sent to differentinterleavers 282 or mappers 283. The transmitting signal processing unit280 may further include a space-time block code (STBC) encoder forspreading the constellation points from the number of spatial streamsinto a number of space-time streams (NsTs) and a spatial mapper formapping the space-time streams to transmit chains. The spatial mappermay use direct mapping, spatial expansion, or beamforming depending onimplementation. When MU-MIMO is employed, one or more of the blocksbefore reaching the spatial mapper may be provided for each user.

The IFT 284 converts a block of the constellation points output from themapper 283 or the spatial mapper into a time domain block (e.g., asymbol) by using an inverse discrete Fourier transform (IDFT) or aninverse fast Fourier transform (IFFT). If the STBC encoder and thespatial mapper are employed, the IFT 284 may be provided for eachtransmit chain.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may insert cyclic shift diversities (CSDs) to preventunintentional beamforming. The CSD insertion may occur before or afterthe inverse Fourier transform operation. The CSD may be specified pertransmit chain or may be specified per space-time stream. Alternatively,the CSD may be applied as a part of the spatial mapper.

The GI inserter 285 prepends a GI to the symbol. The transmitting signalprocessing unit 280 may optionally perform windowing to smooth edges ofeach symbol after inserting the GI. The RF transmitter 221 converts thesymbols into an RF signal and transmits the RF signal via the antennaunit 230. When MIMO or MU-MIMO is employed, the GI inserter 285 and theRF transmitter 221 may be provided for each transmit chain.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processing unit 290 in a wireless communication device.The receiving signal processing unit 290 of the PHY processor 215includes a GI remover 291, a Fourier transformer (FT) 292, a demapper293, a deinterleaver 294, and a decoder 295.

The RF receiver 222 receives an RF signal via the antenna unit 230 andconverts the RF signal into one or more symbols. In some aspects, the GIremover 291 removes the GI from the symbol. When MIMO or MU-MIMO isemployed, the RF receiver 222 and the GI remover 291 may be provided foreach receive chain.

The FT 292 converts the symbol (e.g., the time domain block) into ablock of the constellation points by using a discrete Fourier transform(DFT) or a fast Fourier transform (FFT) depending on implementation. Inone or more implementations, the FT 292 is provided for each receivechain.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may further include a spatial demapper for converting the Fouriertransformed receiver chains to constellation points of the space-timestreams, and a STBC decoder (not shown) for despreading theconstellation points from the space-time streams into the spatialstreams.

The demapper 293 demaps the constellation points output from the FT 292or the STBC decoder to the bit streams. If the LDPC encoding is used,the demapper 293 may further perform LDPC tone demapping before theconstellation demapping. The deinterleaver 294 deinterleaves the bits ofeach stream output from the demapper 293. In one or moreimplementations, deinterleaving may be applied only when BCC decoding isused.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may use multiple instances on the demapper 293 and multipleinstances of the deinterleaver 294 corresponding to the number ofspatial streams. In the example, the receiving signal processing unit290 may further include a stream deparser for combining the streamsoutput from the deinterleavers 294.

The decoder 295 decodes the streams output from the deinterleaver 294and/or the stream deparser. For example, the decoder 295 may be an FECdecoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

FIG. 4 illustrates an example of a timing diagram of interframe space(IFS) relationships. In this example, a data frame, a control frame, ora management frame can be exchanged between the wireless communicationdevices 111-115 and/or other WLAN devices.

Referring to the timing diagram 400, during the time interval 402,access is deferred while the medium (e.g., a wireless communicationchannel) is busy until a type of IFS duration has elapsed. At timeinterval 404, immediate access is granted when the medium is idle for aduration that is equal to or greater than a distributed coordinationfunction IFS (DIFS) 410 duration or arbitration IFS (AIFS) 414 duration.In turn, a next frame 406 may be transmitted after a type of IFSduration and a contention window 418 have passed. During the time 408,if a DIFS has elapsed since the medium has been idle, a designated slottime 420 is selected and one or more backoff slots 422 are decrementedas long as the medium is idle.

The data frame is used for transmission of data forwarded to a higherlayer. In one or more implementations, a WLAN device transmits the dataframe after performing backoff if DIFS 410 has elapsed from a time whenthe medium has been idle.

The management frame is used for exchanging management information thatis not forwarded to the higher layer. Subtype frames of the managementframe include a beacon frame, an association request/response frame, aprobe request/response frame, and an authentication request/responseframe.

The control frame is used for controlling access to the medium. Subtypeframes of the control frame include a request to send (RTS) frame, aclear to send (CTS) frame, and an ACK frame. In the case that thecontrol frame is not a response frame of the other frame (e.g., aprevious frame), the WLAN device transmits the control frame afterperforming backoff if the DIFS 410 has elapsed. In the case that thecontrol frame is the response frame of the other frame, the WLAN devicetransmits the control frame without performing backoff if a short IFS(SIFS) 412 has elapsed. For example, the SIFS may be 16 microseconds.The type and subtype of frame may be identified by a type field and asubtype field in a frame control field of the frame. In an aspect, amicrosecond may be denoted as μs or us.

On the other hand, a Quality of Service (QoS) STA may transmit the frameafter performing backoff if AIFS 414 for access category (AC), e.g.,AIFS[AC], has elapsed. In this case, the data frame, the managementframe, or the control frame that is not the response frame may use theAIFS[AC].

In one or more implementations, a point coordination function (PCF)enabled AP STA transmits the frame after performing backoff if a PCF IFS(PIFS) 416 has elapsed. In this example, the PIFS 416 duration is lessthan the DIFS 410 but greater than the SIFS 412. In some aspects, thePIFS 416 is determined by incrementing the SIFS 412 duration by adesignated slot time 420.

FIG. 5 illustrates an example of a timing diagram of a carrier sensemultiple access/collision avoidance (CSMA/CA) based frame transmissionprocedure for avoiding collision between frames in a channel. In FIG. 5,any one of the wireless communication devices 111-115 in FIG. 1 can bedesignated as one of STA1, STA2 or STA3. In this example, the wirelesscommunication device 111 is designated as STA1, the wirelesscommunication device 112 is designated as STA2, and the wirelesscommunication device 113 is designated as STA3. While the timing of thewireless communication devices 114 and 115 is not shown in FIG. 5, thetiming of the devices 114 and 115 may be the same as that of STA2.

In this example, STA1 is a transmit WLAN device for transmitting data,STA2 is a receive WLAN device for receiving the data, and STA3 is a WLANdevice that may be located at an area where a frame transmitted from theSTA1 and/or a frame transmitted from the STA2 can be received by theSTA3.

The STA1 may determine whether the channel (or medium) is busy bycarrier sensing. The STA1 may determine the channel occupation based onan energy level on the channel or correlation of signals in the channel.In one or more implementations, the STA1 determines the channeloccupation by using a network allocation vector (NAV) timer.

When determining that the channel is not used by other devices duringthe DIFS 410 (e.g., the channel is idle), the STA1 may transmit an RTSframe 502 to the STA2 after performing backoff Upon receiving the RTSframe 502, the STA2 may transmit a CTS frame 506 as a response of theCTS frame 506 after the SIFS 412.

When the STA3 receives the RTS frame 502, the STA3 may set a NAV timerfor a transmission duration representing the propagation delay ofsubsequently transmitted frames by using duration information involvedwith the transmission of the RTS frame 502 (e.g., NAV(RTS) 510). Forexample, the STA3 may set the transmission duration expressed as thesummation of a first instance of the SIFS 412, the CTS frame 506duration, a second instance of the SIFS 412, a data frame 504 duration,a third instance of the SIFS 412 and an ACK frame 508 duration.

Upon receiving a new frame (not shown) before the NAV timer expires, theSTA3 may update the NAV timer by using duration information included inthe new frame. The STA3 does not attempt to access the channel until theNAV timer expires.

When the STA1 receives the CTS frame 506 from the STA2, the STA1 maytransmit the data frame 504 to the STA2 after the SIFS 412 elapses froma time when the CTS frame 506 has been completely received. Uponsuccessfully receiving the data frame 504, the STA2 may transmit the ACKframe 508 after the SIFS 412 elapses as an acknowledgement of receivingthe data frame 504.

When the NAV timer expires, the STA3 may determine whether the channelis busy by the carrier sensing. Upon determining that the channel is notused by the other WLAN devices (e.g., STA1, STA2) during the DIFS 410after the NAV timer has expired, the STA3 may attempt the channel accessafter a contention window 418 has elapsed. In this example, thecontention window 418 may be based on a random backoff.

FIG. 6 illustrates an example of a high efficiency (HE) frame 600. TheHE frame 600 is a physical layer convergence procedure (PLCP) protocoldata unit (or PPDU) format. An HE frame may be referred to as an OFDMAframe, a PPDU, a PPDU format, an OFDMA PPDU, an MU PPDU, another similarterm, or vice versa. An HE frame may be simply referred to as a framefor convenience. A transmitting station (e.g., AP, non-AP station) maygenerate the HE frame 600 and transmit the HE frame 600 to a receivingstation. The receiving station may receive, detect, and process the HEframe 600. The HE frame 600 may include an L-STF field, an L-LTF field,an L-SIG field, an RL-SIG field, an HE-SIG-A field, an HE-SIG-B field,an HE-STF field, an HE-LTF field, and an HE-DATA field. The HE-SIG-Afield may include NHESIGA symbols, the HE-SIG-B field may includeNHESIGB symbols, the HE-LTF field may include NHELTF symbols, and theHE-DATA field may include NDATA symbols. In an aspect, the HE-DATA fieldmay also be referred to as a payload field, data, data signal, dataportion, payload, PSDU, or Media Access Control (MAC) Protocol DataUnits (MPDU) (e.g., MAC frame). A frame may sometimes refer to a PPDU. Aframe may sometimes refer to an MPDU or an A-MPDU.

In one or more implementations, an AP may transmit a frame for downlink(DL) using a frame format shown in this figure or a variation thereof(e.g., without any or some portions of an HE header). A STA may transmita frame for uplink (UL) using a frame format shown in this figure or avariation thereof (e.g., without any or some portions of an HE header).

The table below provides examples of characteristics associated with thevarious components of the HE frame 600.

DFT Subcarrier Element Definition Duration period GI Spacing DescriptionLegacy(L)- Non-high 8 μs — — equivalent to L-STF of a STF throughput1,250 kHz non-trigger- (HT) Short based PPDU Training has a fieldperiodicity of 0.8 μs with 10 periods. L-LTF Non-HT 8 μs 3.2 μs 1.6 μs312.5 kHz Long Training field L-SIG Non-HT 4 μs 3.2 μs 0.8 μs 312.5 kHzSIGNAL field RL-SIG Repeated 4 μs 3.2 μs 0.8 μs 312.5 kHz Non-HT SIGNALfield HE-SIG-A HE N_(HESIGA) * 3.2 μs 0.8 μs 312.5 kHz HE-SIG-A isSIGNAL 4 μs duplicated on A field each 20 MHz segment after the legacypreamble to indicate common control information. N_(HESIGA) means thenumber of OFDM symbols of the HE-SIG-A field and is equal to 2 or 4.HE-SIG-B HE N_(HESIGB) * 3.2 μs 0.8 μs 312.5 kHz N_(HESIGB) SIGNAL 4 μsmeans the B field number of OFDM symbols of the HE-SIG-B field and isvariable. DL MU packet contains HE-SIG-B. Single μser (SU) packets andUL Trigger based packets do not contain HE-SIG-B. HE-STF HE Short 4 or 8μs — — non- HE-STF of a Training trigger- non-trigger- field based basedPPDU PPDU: has a (equivalent periodicity of to) 1,250 0.8 μs with 5 kHz;periods. A non- trigger- trigger-based based PPDU is not PPDU: sent in(equivalent to) response to a 625 kHz trigger frame. The HE-STF of atrigger- based PPDU has a periodicity of 1.6 μs with 5 periods. Atrigger-based PPDU is a UL PPDU sent in response to a trigger frame.HE-LTF HE Long N_(HELTF) * 2xLTF: supports 2xLTF: HE PPDU Training (DFT6.4 μs 0.8, 1.6, (equivalent to) may support field period + 4xLTF: 3.2μs 156.25 kHz; 2xLTF mode GI) μs 12.8 μs 4xLTF: and 4xLTF 78.125 kHzmode. In the 2xLTF mode, HE-LTF symbol excluding GI is equivalent tomodulating every other tone in an OFDM symbol of 12.8 μs excluding GI,and then removing the second half of the OFDM symbol in time domain.N_(HELTF) means the number of HE-LTF symbols and is equal to 1, 2, 4, 6,8. HE-DATA HE DATA N_(DATA) * 12.8 μs supports 78.125 kHz N_(DATA) meansfield (DFT 0.8, 1.6, the number of period + 3.2 μs HE data GI) μssymbols.

Referring to FIG. 6, the HE frame 600 contains a header and a datafield. The header includes a legacy header comprised of the legacy shorttraining field (L-STF), the legacy long training field (L-LTF), and thelegacy signal (L-SIG) field. These legacy fields contain symbols basedon an early design of an IEEE 802.11 specification. Presence of thesesymbols may facilitate compatibility of new designs with the legacydesigns and products. The legacy header may be referred to as a legacypreamble. In one or more aspects, the term header may be referred to asa preamble.

In one or more implementations, the legacy STF, LTF, and SIG symbols aremodulated/carried with FFT size of 64 on a 20 MHz sub-channel and areduplicated every 20 MHz if the frame has a channel bandwidth wider than20 MHz (e.g., 40 MHz, 80 MHz, 160 MHz). Therefore, the legacy field(i.e., the STF, LTF, and SIG fields) occupies the entire channelbandwidth of the frame. The L-STF field may be utilized for packetdetection, automatic gain control (AGC), and coarse frequency-offset(FO) correction. In one aspect, the L-STF field does not utilizefrequency domain processing (e.g., FFT processing) but rather utilizestime domain processing. The L-LTF field may be utilized for channelestimation, fine frequency-offset correction, and symbol timing. In oneor more aspects, the L-SIG field may contain information indicative of adata rate and a length (e.g., in bytes) associated with the HE frame600, which may be utilized by a receiver of the HE frame 600 tocalculate a time duration of a transmission of the HE frame 600.

The header may also include an HE header comprised of an HE-SIG-A fieldand an HE-SIG-B field. The HE header may be referred to as a non-legacyheader. These fields contain symbols that carry control informationassociated with each PLCP service data unit (PSDU) and/or radiofrequency (RF), PHY, and MAC properties of a PPDU. In one aspect, theHE-SIG-A field can be carried/modulated using an FFT size of 64 on a 20MHz basis. The HE-SIG-B field can be carried/modulated using an FFT sizeof e.g., 64 or 256 on a 20 MHz basis depending on implementation. TheHE-SIG-A and HE-SIG-B fields may occupy the entire channel bandwidth ofthe frame. In some aspects, the size of the HE-SIG-A field and/or theHE-SIG-B field is variable (e.g., can vary from frame to frame). In anaspect, the HE-SIG-B field is not always present in all frames. Tofacilitate decoding of the HE frame 600 by a receiver, the size of(e.g., number of symbols contained in) the HE-SIG-B field may beindicated in the HE-SIG-A field. In some aspects, the HE header alsoincludes the repeated L-SIG (RL-SIG) field, whose content is the same asthe L-SIG field.

The HE header may further include HE-STF and HE-LTF fields, whichcontain symbols used to perform necessary RF and PHY processing for eachPSDU and/or for the whole PPDU. The HE-LTF symbols may bemodulated/carried with an FFT size of 256 for 20 MHz bandwidth andmodulated over the entire bandwidth of the frame. Thus, the HE-LTF fieldmay occupy the entire channel bandwidth of the frame. In one aspect, theHE-LTF field may occupy less than the entire channel bandwidth. In oneaspect, the HE-LTF field may be transmitted using a code-frequencyresource. In one aspect, an HE-LTF sequence may be utilized by areceiver to estimate MIMO channel between the transmitter and thereceiver. Channel estimation may be utilized to decode data transmittedand compensate for channel properties (e.g., effects, distortions). Forexample, when a preamble is transmitted through a wireless channel,various distortions may occur, and a training sequence in the HE-LTFfield is useful to reverse the distortion. This may be referred to asequalization. To accomplish this, the amount of channel distortion ismeasured. This may be referred to as channel estimation. In one aspect,channel estimation is performed using an HE-LTF sequence, and thechannel estimation may be applied to other fields that follow the HE-LTFsequence.

The HE-STF symbols may have a fixed pattern and a fixed duration. Forexample, the HE-STF symbols may have a predetermined repeating pattern.In one aspect, the HE-STF symbols do not require FFT processing. The HEframe 600 may include the data field, represented as HE-DATA, thatcontains data symbols. The data field may also be referred to as apayload field, data, payload or PSDU.

In one or more aspects, additional one or more HE-LTF fields may beincluded in the header. For example, an additional HE-LTF field may belocated after a first HE-LTF field. In one or more implementations, a TXsignal processing unit 280 (or an IFT 284) illustrated in FIG. 3A maycarry out the modulation described in this paragraph as well as themodulations described in other paragraphs above. In one or moreimplementations, an RX signal processing unit 290 (or an FT 292) mayperform demodulation for a receiver.

FIG. 7 illustrates an example of an HEW PPDU. The L-STF field may beutilized to perform frequency offset estimation and phase offsetestimation for preamble decoding at a legacy station (STA) (e.g., astation that is in compliance with IEEE 802.11a, g, n, and/or ac(hereafter IEEE 802.11a/b/g/n/ac)). The L-LTF field may be utilized toperform channel estimation for preamble decoding at a legacy STA. TheL-SIG field may be utilized for the preamble decoding at the legacy STAand may provide protection against PPDU transmission by a third party(e.g., a third party station is not allowed to transmit during a certainperiod based on the value of a LENGTH field included in the L-SIGfield).

The HE-SIG-A field (or HEW SIG-A field) may include HEW PPDU modulationparameters or the like for HEW preamble decoding at an HEW STA (e.g., astation that is in compliance with IEEE 802.11ax). In an aspect, an HEWSTA may be referred to as an HE STA, HE-based STA, STA, user, terminal,or variant thereof. The parameters in the HEW SIG-A field may includevery high throughput (VHT) PPDU modulation parameters, as listed in thetables below, so as to realize backward compatibility with legacy STAs(e.g., IEEE 802.11ac terminals).

The tables below illustrate fields, bit positions, number of bits, anddescriptions included in each of two parts, VHT-SIG-A1 and VHT-SIG-A2,of the VHT-SIG-A field defined in the IEEE 802.11ac standard. Forexample, a bandwidth (BW) field occupies two least significant bits(LSBs), B0 and B1, of the VHT-SIG-A1 field and has a size of 2 bits. Ifthe 2 bits are set to 0, 1, 2, or 3, the BW field indicates 20 MHz, 40MHz, 80 MHz, or 160 MHz and 80+80 MHz. For details of the fieldsincluded in the VHT-SIG-A field, refer to the IEEE 802.11ac-2013technical specification (hereafter IEEE 802.11ac specification), whichis incorporated herein by reference. In some aspects, in the HE PPDUframe format, the HE-SIG-A field may include one or more of the fieldsincluded in the VHT-SIG-A field, and the HE-SIG-A field mayprovide/facilitate backward compatibility with IEEE 802.11ac stations.

The table below illustrates fields, bit positions, number of bits, anddescriptions included in VHT-SIG-A1.

Number Bit Field of bits Description B0-B1 BW 2 Set to 0 for 20 MHz, 1for 40 MHz, 2 for 80 MHz, and 3 for 160 MHz and 80 + 80 MHz B2 Reserved1 Reserved. Set to 1. B3 STBC 1 For a VHT SU PPDU:   Set to 1 if spacetime block coding is used and set to 0 otherwise. For a VHT MU PPDU:  Set to 0. B4-B9 Group ID 6 Set to the value of the TXVECTOR parameterGROUP_ID. A value of 0 or 63 indicates a VHT SU PPDU; otherwise,indicates a VHT MU PPDU. B10-B21 NSTS/ 12 For a VHT MU PPDU: NSTS isdivided into 4 user Partial AID positions of 3 bits each. User positionp, where 0 ≤ p ≤ 3, uses bits B(10 + 3p) to B(12 + 3p). The number ofspace-time streams for user u are indicated at user position p =USER_POSITION[u] where u = 0, 1, . . . , NUM_USERS − 1 and the notationA[b] denotes the value of array A at index b. Zero space-time streamsare indicated at positions not listed in the USER_POSITION array. Eachuser position is set as follows:   Set to 0 for 0 space-time streams.  Set to 1 for 1 space-time stream   Set to 2 for 2 space-time streams  Set to 3 for 3 space-time streams   Set to 4 for 4 space-time streams  Values 5-7 are reserved For a VHT SU PPDU: B10-B12   Set to 0 for 1space-time streams.   Set to 1 for 2 space-time stream   Set to 2 for 3space-time streams   Set to 3 for 4 space-time streams   Set to 4 for 5space-time streams   Set to 5 for 6 space-time streams   Set to 6 for 7space-time streams   Set to 7 for 8 space-time streams B13-B21   PartialAID: Set to the value of the TXVECTOR   parameter PARTIAL_AID. PartialAID   provides an abbreviated indication of the   intended recipient(s)of the PSDU (see 9.17a   (Group ID and partial AID in VHT PPDUs) of  the IEEE 802.11ac specification). B22 TXOP_PS_NOT_ALLOWED 1 Set to 0by VHT AP if it allows non-AP VHT STAs in TXOP power save mode to enterDoze state during a TXOP. Set to 1 otherwise. The bit is reserved andset to 1 in VHT PPDUs transmitted by a non-AP VHT STA. B23 Reserved 1Set to 1

The table below illustrates fields, bit positions, number of bits, anddescriptions included in VHT-SIG-A2.

Number Bit Field of bits Description B0 Short GI 1 Set to 0 if shortguard interval is not used in the Data field. Set to 1 if short guardinterval is used in the Data field. B1 Short GI 1 Set to 1 if shortguard interval is used and N_(SYM) mod N_(SYM) 10 = 9; otherwise, set to0. N_(SYM) is defined in 22.4.3 Disambiguation (TXTIME and PSDU_LENGTHcalculation) of the IEEE 802.11ac specification. B2 SU/MU[0] 1 For a VHTSU PPDU, B2 is set to 0 for BCC, 1 for Coding LDPC. For a VHT MU PPDU,if the MU[0] NSTS field is nonzero, then B2 indicates the coding usedfor user u with USER_POSITION[u] = 0; set to 0 for BCC and 1 for LDPC.If the MU[0] NSTS field is 0, then this field is reserved and set to 1.B3 LDPC Extra 1 Set to 1 if the LDPC PPDU encoding process (if an OFDMSU PPDU), or at least one LDPC user's PPDU Symbol encoding process (if aVHT MU PPDU), results in an extra OFDM symbol (or symbols) as describedin 22.3.10.5.4 (LDPC coding) and 22.3.10.5.5 (Encoding process for VHTMU PPDUs) of the IEEE 802.11ac specification. Set to 0 otherwise. B4-B7SU VHT- 4 For a VHT SU PPDU: MCS/MU[1-3]   VHT-MCS index Coding For aVHT MU PPDU:   If the MU[1] NSTS field is nonzero, then B4   indicatescoding for user u with   USER_POSITION[u] = 1; set to 0 for BCC, 1   forLDPC. If the MU[1] NSTS field is 0, then B4   is reserved and set to 1.  If the MU[2] NSTS field is nonzero, then B5   indicates coding foruser u with   USER_POSITION[u] = 2; set to 0 for BCC, 1   for LDPC. Ifthe MU[2] NSTS field is 0, then B5   is reserved and set to 1.   If theMU[3] NSTS field is nonzero, then B6   indicates coding for user u with  USER_POSITION[u] = 3; set to 0 for BCC, 1   for LDPC. If the MU[3]NSTS field is 0, then B6   is reserved and set to 1.   B7 is reservedand set to 1. B8 Beamformed 1 For a VHT SU PPDU:   Set to 1 if aBeamforming steering matrix is   applied to the waveform in an SUtransmission   as described in 20.3.11.10.1 (Spatial mapping) of theIEEE 802.11n specification.   Set to 0 otherwise. For a VHT MU PPDU:  Reserved and set to 1. NOTE - If equal to 1 smoothing is notrecommended. B9 Reserved 1 Reserved and set to 1. B10-B17 CRC 8 CRC ascalculated in 20.3.9.4.4 (CRC calculation for HT-SIG) of the IEEE802.11n specification with c7 in B10. Bits 0-23 of HT-SIG1 and bits 0-9of HT- SIG2 are replaced by bits 0-23 of VHT-SIG-A1 and bits 0-9 ofVHT-SIG-A2, respectively. B18-B23 Tail 6 Used to terminate the trellisof the convolutional decoder. Set to 0.

In some aspects, the HEW PPDU format may be utilized to support MUMIMO-OFDMA. In such aspects, information about sub-channels allocated torespective HEW STAs may be included in the HEW SIG-A field. In anaspect, information about a sub-channel allocated to an HEW STA may beconfigured by including a Sub-channel Allocation Structure (SAS) fieldin the HEW SIG-A field.

In an aspect, the SAS field may include a plurality of sub-channelbandwidth units. For example, if a sub-channel bandwidth unit is 3 bits,0 may indicate 5 MHz, 1 may indicate 10 MHz, 2 may indicate 20 MHz, 3may indicate 40 MHz, 4 may indicate 80 MHz, and 5 may indicate 160 MHz.In this case, if a sub-channel allocation structure is configured bydividing an up to 160-MHz channel into sub-channels of at least 5 MHzeach, the SAS field needs a total of 96 bits (=3×32). In order to reducethe signaling overhead of the SAS field, a sub-channel allocationstructure may be determined independently for each 20-MHz channel, andif a different SAS field may be included in an HEW SIG-A on a 20-MHzchannel basis, only 12 bits (=3×4) are required.

FIG. 8 illustrates an example of a 40-MHz HEW PPDU. In this example, theSAS fields in the HEW SIG-A fields are set to {0, 0, 1} and {0, 0, 0, 0}for 20-MHz channels of the 40-MHz HEW PPDU. As provided previously as anexample, 0 may indicate 5 MHz and 1 may indicate 10 MHz, in which casethe SAS fields of FIG. 8 indicate that 5 MHz, 5 MHz, 10 MHz, 5 MHz, 5MHz, 5 MHz, and 5 MHz sub-channels are defined from 20-MHz channels.Upon receipt of the 40-MHz HEW PPDU, a STA may receive the HEW-STF,HEW-LTF, and HEW SIG-B fields on the respective 5 MHz, 5 MHz, 10 MHz, 5MHz, 5 MHz, 5 MHz, and 5 MHz sub-channels, and may determine asub-channel to be received by determining destination STAs of therespective sub-channels.

In an aspect, in such an HEW PPDU transmission, sub-channels allocatedto the respective HEW STAs are sequential to each other and, as aresult, empty sub-channels, which are not allocated, are not presentwithin a single 20 MHz channel. Furthermore, in an aspect, sub-channelsallocated to the respective HEW STAs are implemented only in a singlechannel on a 20 MHz channel basis. Consequently, in each of multiple 20MHz channels, the allocation of partially overlapping sub-channels isprohibited. This means that, since the upper and lower 20-MHz channelsare partially overlapped with each other, sub-channels are not allocatedin FIG. 8.

In an aspect, upon receipt of the HEW-STF, HEW-LTF, and HEW SIG-B fieldson the respective sub-channels, a STA may determine a sub-channel to bereceived as a destination STA based on the Partial AID and Group IDfields included in the HEW SIG-B fields.

FIG. 9 illustrates an example of an HEW PPDU. The HEW PPDU may beassociated with four 5-MHz sub-channels. Partial AIDs may be included inHEW SIG-B fields of respective sub-channels to indicate (e.g., provideidentifiers (IDs) that identify) destination STAs. In FIG. 9, thePartial AIDs are set to 1, 2, 3, and 4 in the HEW PPDU. If the PartialAIDs of STA1, STA2, STA3, and STA4 are 1, 2, 3, 4, respectively, STA1,STA2, STA3, and STA4 receive PSDUs directed to them on sub-channels withthe Partial AID values in the PSDUs matching their respective PartialAID.

In an aspect, Partial AIDs are not unique for STAs. In such an aspect,STAs having the same Partial AID should not exist among the destinationSTAs of the HEW PPDU. FIG. 10 illustrates an example of an HEW PPDU inwhich two Partial AIDs included in the HEW SIG-B fields of respectivesub-channels are equal. The HEW PPDU is associated with four 5-MHzsub-channels. In FIG. 10, the Partial AIDs are set to 1, 2, 3, and 1,respectively. If the Partial AIDs of STA1, STA2, STA3, and STA4 are 1,2, 3, 1, respectively, STA2 and STA3 may receive PSDUs directed to themon sub-channels with the Partial AID values of the PSDUs matching theirrespective Partial AID. However, in an aspect, each of STA1 and STA4does not identify a sub-channel to be received because there aremultiple sub-channels with Partial AIDs matching the station's PartialAID (e.g., multiple sub-channels with Partial AID of 1). In other words,in this aspect, although the AP transmits PSDUs to different destinationSTAs on different sub-channels, the destination STAs that have the samePartial AID (e.g., STA1 and STA4 in FIG. 10) does not identifysub-channels to be received.

FIG. 11 illustrates an example of an HEW PPDU in which Group IDsincluded in the HEW SIG-B field of each respective sub-channel, whichare IDs indicating destination STAs of the respective sub-channels, areset to 1, 2, 3, and 4. This case may correspond to transmission of anMU-MIMO frame in an HEW PPDU. In this case, the STAs having membershipof Group ID 1 are STA1 and STA2, STAs having membership of Group ID 2are STA3 and STA4, STAs having membership of Group ID 3 are STA5 andSTA6, and STAs having membership of Group ID 4 are STA7 and STA8. Eachof STA1, STA2, STA3, STA4, STA5, STA6, STA7, and STA8 may compare theGroup ID values contained in the HEW SIG-B fields with its Group IDmembership status. If the STA has membership of a Group ID, the STAreceives a PSDU on a sub-channel carrying the Group ID.

In an aspect, STAs may have membership of multiple Group IDs. FIG. 12illustrates an example of such an HEW PPDU. In FIG. 12, STAs havingmembership of Group ID 1 are STA1 and STA2, STAs having membership ofGroup ID 2 are STA3 and STA4, STAs having membership of Group ID 3 areSTA5 and STA6, and STAs having membership of Group ID 5 are STA1, STA9,and STA10. Thus, STA1 has membership of Group ID 1 and Group ID 5. InFIG. 12, among the STAs having membership of Group ID 5, the APtransmits an MU-MIMO frame to STA9 and STA10 (e.g., the stations havingmembership of Group ID 5 except for STA1). Each of STA2, STA3, STA4,STA5, STA6, STA9, and STA10 may compare the Group ID value of each HEWSIG-B field with its Group ID membership status. If the STA hasmembership of a Group ID, the STA receives a PSDU on a sub-channelcarrying the Group ID. In an aspect, although the AP may transmit PSDUsto different destination STAs on different sub-channels, a STA havingmembership of different Group IDs included in the HEW SIG-B fields(e.g., STA1 in FIG. 12), the STA does not identify a sub-channel to bereceived. Therefore, in this aspect, Group IDs to which a STA commonlybelongs (among multiple Group IDs indicating destination STAs in the HEWSIG-B fields of an HEW PPDU) should not be included as IDs indicatingdestination STAs of MU-MIMO transmission in the HEW PPDU. In FIG. 12,such Group IDs include Group ID 1 and Group ID 5. These two Group IDsshould not be scheduled simultaneously for MU-MIMO frame transmission inan HEW PPDU.

FIG. 13 illustrates an example of an HEW PPDU in which both an SU-MIMOframe and an MU-MIMO frame are transmitted. The HEW PPDU has four 5-MHzsub-channels. In FIG. 13, Group IDs included in the HEW SIG-B fields ofthe lower two sub-channels are set to 1 and 2, respectively, and PartialAIDs included in the HEW SIG-B fields of the upper two sub-channels areset to 1 and 2, respectively. In this case, an MU-MIMO frame istransmitted on the lower two sub-channels to STAs having membership ofGroup ID 1 (STA1 and STA2), and STAs having membership of Group ID 2(STA3 and STA4). Each of STA3 and STA4 may compare the Group IDs valuesof the HEW SIG-B fields with its Group ID membership status. If the STAhas membership of a Group ID, the STA may receive a PSDU on asub-channel carrying the Group ID.

Also, in this case, an SU-MIMO frame may be transmitted on the upper twosub-channels. For example, if the Partial AIDs of STA1, STA2, STA3,STA4, STA5, and STA6 are 1, 2, 3, 4, 1, and 2, respectively, STA5 andSTA6 receive PSDUs destined/intended for them on sub-channels withPartial AIDs values in the HEW SIG-B fields matching their Partial AIDs.In this example, STA1 and STA2 may face a problem. STA1 and STA2 areaware that the Partial AID values of the HEW SIG-B fields included inthe corresponding sub-channels are equal to their Partial AIDs in thePSDUs transmitted to STA5 and STA6 by the AP. However, since STA1 andSTA2 have membership of Group ID on the lower sub-channels with Group ID1 carrying the MU-MIMO frame transmitted, STA1 and STA2 recognize thatthey should receive the corresponding PSDUs. In an aspect, although theAP may transmit PSDUs to different destination STAs on differentsub-channels, destination STAs having the same Partial AID of the sameGroup ID does not identify sub-channels to be received. In FIG. 13, suchSTAs are STA1 and STA2, and these two STAs may not identify sub-channelsto be received. To avert this problem, in an aspect, Group IDs to whichSTAs having a Partial AID value equal to a corresponding Partial AID(among Partial AIDs and Group IDs included in HEW SIG-B fields of an HEWPPDU) should not be included as IDs indicating destination STAs ofSU-MIMO transmission and MU-MIMO transmission in the HEW PPDU. In otherwords, since STA1 has membership of Group ID 1 and has Partial AID 1, anSU-MIMO frame with Partial AID 1 and an MU-MIMO frame for Group ID 1should not be transmitted simultaneously in one HEW PPDU.

In some aspects, alternatively or in addition, an HEW PPDU may include aPartial AID and a Group ID in fields other than the HEW SIG-B field.Depending on implementation, an HEW SIG-A field and/or HEW SIG-C fieldmay include a Partial AID and a Group ID. Further, while a Partial AIDand a Group ID are given as IDs indicating destination STAs of SU-MIMOtransmission and MU-MIMO transmission in one aspect, they may identifydestination STAs of an OFDMA resource allocation in another aspect.

In an aspect, an HEW PPDU format may be provided that can support MUMIMO-OFDMA. In this aspect, the HEW SIG-B field may include informationabout the numbers of spatial streams to be transmitted to HEW STAsallocated to respective sub-channels.

FIG. 14 illustrates an example of an HEW PPDU for MIMO-OFDMAtransmission. In FIG. 14, a first 5 MHz sub-channel is allocated to STA1and STA2 and two spatial streams are transmitted to each STA in adownlink MU-MIMO or OFDMA manner (e.g., a total of four spatial streamsare transmitted on one sub-channel). For this purpose, an HEW-STF,HEW-LTF, HEW-SIG-B, HEW-LTF, HEW-LTF, HEW-LTF, HEW-LTF, and HEW SIG-Cfield follow the HEW-SIG-A field on the sub-channel. The HEW-STF may beused for frequency offset estimation and phase offset estimation for the5 MHz sub-channel. The HEW-LTF may be used for channel estimation forthe 5 MHz sub-channel. Since the sub-channel carries four spatialstreams, as many HEW-LTFs (e.g., HEW-LTF symbols or HEW-LTF elements inan HEW-LTF section) as the number of special streams are transmitted tofacilitate MIMO transmission. In other words, four HEW-LTFs aretransmitted in order to enable/support MIMO transmission (e.g., MU-MIMOtransmission).

In an aspect, a relationship between a total number of spatial streamstransmitted on one sub-channel and a number of HEW-LTFs transmitted islisted in the table below. For instance, as shown in the table, when thetotal number of spatial streams to be transmitted is three, a total offour HEW-LTFs are transmitted.

Total number of spatial streams transmitted on one sub-channel Number ofHEW-LTFs 1 1 2 2 3 4 4 4 5 6 6 6 7 8 8 8

Referring to the table above, if one spatial stream is transmitted onone sub-channel, at least one HEW-LTF is (e.g., needs to be) transmittedon the sub-channel. If an even number of spatial streams are transmittedon one sub-channel, at least as many HEW-LTFs as the number of spatialstreams are transmitted. If an odd number of spatial streams greaterthan one are transmitted on one sub-channel, at least as any HEW-LTFs asa number of adding 1 to the number of spatial streams are transmitted.

In FIG. 14, a second 5 MHz sub-channel is allocated to STA3 and STA4 andone spatial stream per STA is transmitted in the downlink MU-MIMO orOFDMA manner (e.g., a total of two spatial streams are transmitted onone sub-channel). In this case, two HEW-LTFs are transmitted on thesecond sub-channel, however, in the example of FIG. 14, the HEW-STF,HEW-LTF, HEW-SIG-B, HEW-LTF, HEW-LTF, HEW-LTF, HEW-LTF, and HEW SIG-Cfield follow the HEW-SIG-A field.

In the foregoing description, in an aspect, when the total number ofspatial streams to be transmitted is two, a total of two HEW-LTFs aretransmitted. However, in an aspect, in the second 5 MHz sub-channeltransmitted to STA3 and STA4, a total of four HEW-LTFs are transmitted.In an aspect, this operation is intended to add a separate condition inrelation to the HEW-LTF transmission, and is configured to cause thestarting times of transmission of PSDUs that are transmitted indifferent sub-channels to coincide with each other. If the number ofHEW-LTFs substantially required in the second 5 MHz sub-channel (e.g.,only two HEW-LTFs) are transmitted, a problem may arise in that thestarting times of PSDU transmission in the first 5 MHz sub-channel andin the second 5 MHz sub-channel differ from each other.

In one aspect, an HEW-LTF transmission rule may be added to obviate thisproblem. For all HEW STAs allocated to respective sub-channels (e.g.,for SU-MIMO transmission, a single HEW STA; for MU-MIMO transmission,multiple HEW STAs that are destination terminals of MU-MIMOtransmission), the number of HEW-LTFs to be transmitted through each ofother sub-channels is set to the same number as the number of HEW-LTFsin the sub-channel requiring the largest number of HEW-LTFs, among allof the numbers of HEW-LTFs required depending on the numbers of spatialstreams to be transmitted through respective sub-channels.

Through the application of this rule, in the above example, a third 5MHz sub-channel may be allocated to STA5 and one spatial stream may betransmitted through the corresponding sub-channel in an SU-MIMO manner.However, as shown in FIG. 14, even if it is actually sufficient totransmit only a single HEW-LTF, a total of four HEW-LTFs are transmittedto match the number of HEW-LTFs to be transmitted through othersub-channels.

Further, in the above example, a fourth 5 MHz sub-channel is allocatedto STA6 and one spatial stream is transmitted through the correspondingsub-channel in the SU-MIMO manner. However, as shown in FIG. 14, even ifit is actually sufficient to transmit only a single HEW-LTF, a total offour HEW-LTFs are transmitted to match the number of HEW-LTFs to betransmitted through other sub-channels.

In an aspect, in order for the HEW PPDU format to support MU-MIMO,independent signaling information may need to be transmitted througheach sub-channel. In the case of MU-MIMO, different numbers of spatialstreams may be transmitted to multiple HEW STAs, which are destinationterminals of MU-MIMO transmission. For this purpose, in an aspect,information about the number of spatial streams to be transmitted toeach of the HEW STAs is transferred. If the maximum number of spatialstreams that can be transferred to a single HEW STA via MU-MIMOtransmission is 4, and the maximum number of destination terminals ofMU-MIMO transmission is 4, a total of 12 bits may be required for eachsub-channel. When a maximum of four sub-channels can be configured in a20 MHz channel, a total of 48 bits of signaling information may berequired. Therefore, to reduce protocol overhead, such spatial streamallocation information for each sub-channel may be independentlytransmitted.

FIG. 15 illustrates an example of an HEW PPDU. The HEW SIG-B field mayinclude spatial stream allocation information for each sub-channel, andmay indicate the number of spatial streams (NsTs) to be transmitted toSTAs belonging to the corresponding group (group ID) of MU-MIMO in theform of a group ID and NsTs. A signal field (e.g., HEW-SIG-C field)transmitted after the HEW-LTFs may include modulation and coding scheme(MCS) information and PSDU length information for each PSDU.

In an aspect, an HEW-SIG-B field and an HEW-SIG-A field in combinationare described. However, the description applies to a modification inwhich the afore-described HEW-SIG-B field is separated from the HEWSIG-A field and transmitted after an HEW-STF field and an HEW-LTF field.

FIG. 16 illustrates an example of an HEW PPDU. In an aspect, each of theL-STF, L-LTF, L-SIG, and HEW SIG-A fields is composed of OFDM symbolshaving a length of 4.0 μs based on 64-Fast Fourier Transform (FFT). Atthis time, a single OFDM symbol has a guard interval (GI) value of 0.8μs, denoted as G1.

Each of the HEW-STF, HEW-LTF, HEW SIG-B, and PSDU that are subsequentlytransmitted may be composed of OFDM symbols having a length of 16 μsbased on 256 FFT (but the duration of an OFDM symbol may vary with theGI value). In this case, a single OFDM symbol may have two GI values forrespective guard intervals. The first guard interval is the valueapplied to the OFDM symbols of the HEW-STF, HEW-LTF, and HEW SIG-B,denoted as G2. The second guard interval is the value applied to theOFDM symbols of the PSDU, denoted as G3. G2 and G3 may be eitheridentical to each other or different from each other. Further, unlikeG1, the values of G2 and G3 are variable depending on respective PPDUtransmission vectors that are transmitted, without being fixed. Forexample, in an aspect, when G1 is fixed at 0.8 μs, G2 may be randomlyselected from among 3.2 μs, 1.6 μs, 0.8 μs, and 0.4 μs. Similarly, G3may also be randomly selected from among 3.2 μs, 1.6 μs, 0.8 μs, and 0.4μs. Further, the HEW SIG-A field may include signaling information forindicating the selected G2 and G3 values. Once the G2 and G3 values areselected, they are applied in common to all OFDM symbols that aretransmitted during the corresponding interval, or to all sub-channels.

In an aspect, when G2 and G3 values are different from each other, aproblem may arise in that, if the transmission times of PSDUs do notcoincide with each other, OFDM symbol timing, at which OFDM symbols aretransmitted through respective sub-channels, is not synchronized.However, in FIG. 16, the transmission times of the PSDUs through therespective sub-channels coincide with each other, and thus no problem iscaused by the G2 and G3 values.

In one aspect, a method for synchronizing OFDM symbol timing at whichOFDM symbols are transmitted through respective sub-channels is providedfor in the situation in which PSDU transmission times do not coincidewith each other. In FIG. 16, the length of the interval to which theguard interval G2 of the HEW PPDU format is applied is designated to bevariable. That is, the lengths of the transmission intervals for theHEW-STF, HEW-LTF, and HEW SIG-B fields are variable depending on thePPDU transmission vectors to be transmitted.

However, the interval to which the guard interval G2 of the HEW PPDUformat is applied to the HEW-STF and HEW-LTF may be fixed. FIG. 17illustrates an example of an HEW PPDU in which the guard interval G2 isfixed. Depending on the implementation, the interval to which the guardinterval G2 is applied may be limited only to HEW-STF. Further,depending on the implementation, the interval may be limited to therange above HEW-STF. Furthermore, depending on the implementation, theinterval to which guard interval G2 is applied may be limited to 0.After the corresponding interval to which the guard interval G2 isapplied, guard interval G3 is equally applied to 0 or one or more of theHEW-LTFs, the HEW SIG-B, and the PSDU for respective sub-channelsdepending on the transmission vectors for respective sub-channels.

In an aspect, to reduce the decoding complexity of the destinationterminal, the guard interval value for the first OFDM symbol transmittedsubsequent to the HEW SIG-A field (e.g., guard interval G2) is set to afixed value. Unlike G1 and G2, G3 may be a variable value, rather than afixed value, depending on the individual PPDU transmission vectors thatare transmitted. For example, when G1 is fixed at 0.8 μs and G2 is fixedat one of 3.2 μs, 1.6 μs, 0.8 μs, and 0.4 μs, G3 may be randomlyselected from among 3.2 μs, 1.6 μs, 0.8 μs, and 0.4 μs, and signalinginformation for indicating the selected G3 value may be included in theHEW SIG-A field.

FIG. 18 illustrates an example of an HEW PPDU. In an aspect, theaforementioned HEW PPDU format for allowing PSDU transmission times tocoincide with each other may be extended to the format for two or more20 MHz channels. In an aspect, when the format is extended to 40/80/160MHz channel bandwidth, no portion in the HEW PPDU format is revised and,for respective 20 MHz channels, OFDM symbol durations (SDs) and guardintervals are identical.

In the 20 MHz channel shown in the lower portion of FIG. 18, the OFDMsymbol duration and guard interval of L-STF, L-LTF, L-SIG, and HEW SIG-Aare S1 and G1, respectively. In a similar manner, in this case, in the20 MHz channel in the upper portion of FIG. 18, the OFDM symbol durationand guard interval of L-STF, L-LTF, L-SIG, and HEW SIG-A are S1 and G1,respectively.

In the 20 MHz channel in the lower portion of FIG. 18, the OFDM symbolduration and guard interval of the HEW-STF, HEW-LTF, and HEW SIG-A areS2 and G2, respectively. In a similar matter, in this case, in the 20MHz channel in the upper portion, the OFDM symbol duration and guardinterval of the HEW-STF, HEW-LTF, and HEW SIG-A are S2 and G2,respectively.

In the 20 MHz channel in the lower portion of FIG. 18, the OFDM symbolduration and guard interval of the PSDU are S3 and G3, respectively. Ina similar matter, in this case, in the 20 MHz channel in the upperportion, the OFDM symbol duration and guard interval of the PSDU are S3and G3, respectively.

If the OFDM symbol duration and guard interval are configured and usedfor transmission based on 64 FFT in any one 20 MHz channel, the OFDMsymbol duration and guard interval are configured and used fortransmission based on 64 FFT in the remaining 20 MHz channel. In anaspect, if the OFDM symbol duration and guard interval are configuredand used for transmission based on 64 FFT in any one 20 MHz channel, itmay not be possible to configure and use the OFDM symbol duration andguard interval for transmission based on 256 FFT in the remaining 20 MHzchannel.

Depending on the implementation, the OFDM symbol duration and guardinterval values in the respective 20 MHz channels (e.g., S2 and G2, S3and G3 in FIG. 18) may be set to different values for respective 20 MHzchannels. For reference, S1 and G1 are fixed for all 20 MHz channels.Even in this case, in a single 20 MHz channel, the same values areapplied to S2, G2, S3, and G3 for respective sub-channels.

In one or more aspects, an HEW PPDU format is provided for 40/80/160 MHzchannel bandwidth. FIG. 19 illustrates an HEW PPDU format. In an aspect,the aforementioned HEW PPDU format in which PSDU transmission times donot coincide with each other may be extended to the format for two ormore 20 MHz channels. In an aspect, when the format is extended to40/80/160 MHz channel bandwidth, no portion in the HEW PPDU format isrevised and, for respective 20 MHz channels, OFDM symbol durations andguard intervals are identical.

In the 20 MHz channel shown in the lower portion of FIG. 19, the OFDMsymbol duration and guard interval of the L-STF, L-LTF, L-SIG, and HEWSIG-A are S1 and G1, respectively. In a similar manner, in this case, inthe 20 MHz channel in the upper portion, the OFDM symbol duration andguard interval of the L-STF, L-LTF, L-SIG, and HEW SIG-A are S1 and G1,respectively.

In the 20 MHz channel in the lower portion of FIG. 19, the OFDM symbolduration and guard interval of the HEW-STF and HEW-LTF are S2 and G2,respectively. In a similar manner, in this case, in the 20 MHz channelin the upper portion, the OFDM symbol duration and guard interval of theHEW-STF and HEW-LTF are S2 and G2, respectively.

In the 20 MHz channel in the lower portion of FIG. 19, the OFDM symbolduration and guard interval are S3 and G3, respectively, for the periodduring which 0 or one or more HEW-LTFs, HEW SIG-B, and PSDU aretransmitted depending on the transmission vectors for respectivesub-channels. In a similar manner, in this case, in the 20 MHz channelin the upper portion, the OFDM symbol duration and guard interval of theHEW-LTF, HEW SIG-B, and PSDU are also S3 and G3, respectively.

In an aspect, if the OFDM symbol duration and guard interval areconfigured and used for transmission based on 64 FFT in any one 20 MHzchannel, the OFDM symbol duration and the guard interval are configuredand used for transmission based on 64 FFT in the remaining 20 MHzchannel. In an aspect, when the OFDM symbol duration and the guardinterval are configured and used for transmission based on 64 FFT in anyone 20 MHz channel, it may not be possible to configure and use the OFDMsymbol duration and the guard interval for transmission based on 256 FFTin the remaining 20 MHz channel.

Depending on the implementation, the OFDM symbol duration values andguard interval values in the respective 20 MHz channels (e.g., S2, G2,S3, and G3 in FIG. 19) may be set to different values for respective 20MHz channels. For reference, S1 and G1 are fixed for all 20 MHzchannels. Even in this case, in a single 20 MHz channel, the same valuesare applied to S2, G2, S3, and G3 for respective sub-channels.

In an aspect, performance may be further improved by applying MU-MIMOtechnology when multiple terminals perform simultaneous transmission toa single AP. Uplink MU-MIMO technology is applicable to the case wherethe AP is capable of simultaneously receiving multiple spatial streamsthrough multiple antennas.

FIG. 20 illustrates an example in which STA1, STA2, STA3, and STA4simultaneously transmit uplink data frames to the AP. In an aspect, in aprocedure for performing simultaneous transmission via uplink MU-MIMOtechnology, a signaling procedure may be conducted in advance (e.g.,prior to the simultaneous transmission of uplink data frames) in whichthe AP determines the terminals that are sources of uplink data frametransmission and designates the numbers of spatial streams transmittableby the corresponding terminals and the guard intervals to be used forPSDU transmission. FIG. 20 illustrates the case where the AP determinesSTA1, STA2, STA3, and STA4 to be the terminals that are sources ofuplink data frame transmission, and designates the numbers of spatialstreams transmittable by the corresponding stations as 4, 2, 1, and 1,respectively.

In an aspect, the L-STF, L-LTF, L-SIG, and HEW SIG-A fields may havecommon values when STA1, STA2, STA3, and STA4 simultaneously transmituplink data frames to the AP. In an aspect, if these fields do not havecommon values, the AP may be incapable of correctly receiving thecorresponding fields. The HEW SIG-A fields may include information aboutSTA1, STA2, STA3, and STA4 and the numbers of spatial streamstransmittable by the corresponding stations, thus allowing the stationsto correctly receive the HEW-STF, HEW-LTF, HEW SIG-B, and PSDU.

In FIG. 20, the AP designated the numbers of transmittable spatialstreams of STA1, STA2, STA3, and STA4 as 4, 2, 1, and 1, respectively.If STA1, STA2, STA3, and STA4 transmit PSDUs in conformity with thenumbers of transmittable spatial streams designated by the AP, spatialstream information such as 4 spatial streams, 2 spatial streams, 1spatial stream, and 1 spatial stream may be included in the HEW SIG-Afields (e.g., only in the HEW SIG-A fields). In an aspect, STA1, STA2,STA3, and STA4 may randomly select the numbers of spatial streams to betransmitted (e.g., under the condition that the randomly selected numberdoes not exceed the number of transmittable spatial streams designatedby the AP). For instance, if 2 spatial streams, 1 spatial stream, 1spatial stream, and 1 spatial stream are respectively used for actualPSDU transmission, such information about the corresponding spatialstreams may need to be included in the HEW SIG-B fields for indicatinguser-specific information. In other words, pieces of information aboutthe numbers of spatial streams (e.g., 4, 2, 1, and 1) are included inthe HEW SIG-A fields, and function to indicate the HEW-STF and thenumbers of HEW-LTFs. As shown in FIG. 20, when the numbers of HEW-LTFstransmitted by the terminals are identical to each other, informationabout the total number of HEW-LTFs actually transmitted (e.g., 4) may beincluded in each HEW SIG-A field without individually indicating 4spatial streams, 2 spatial streams, 1 spatial stream, and 1 spatialstream. Further, pieces of information about the 2 spatial streams, 1spatial stream, 1 spatial stream, and 1 spatial stream may be includedin respective HEW SIG-B fields, thus indicating the numbers of spatialstreams that are actually used for PSDU transmission.

Even in uplink MU-MIMO transmission, when the starting times of PSDUtransmission are different from each other, the problem of misalignmentbetween OFDM symbols may arise. To solve this problem, a method may beutilized to cause the numbers of HEW-LTFs transmitted in uplink MU-MIMOfor all terminals to be identical to each other. In FIG. 20, theterminals require the transmission of 4, 2, 1, and 1 HEW-LTFs,respectively, in uplink data frame transmission. To adjust the numbersof HEW-LTFs that are transmitted to be identical to each other for thedifferent terminals, 0, 2, 3, and 3 HEW-LTFs may be additionallytransmitted, respectively.

In FIG. 20, the L-STF, L-LTF, L-SIG, and HEW SIG-A fields aretransmitted using guard interval G1, the HEW-STF, HEW-LTF, and HEW SIG-Bfields are transmitted using guard interval G2, and the PSDU istransmitted using guard interval G3. The guard intervals G2 and G3 maybe implemented using fixed values or variable values. If the guardintervals G2 and G3 are variable, information indicating the values ofthe guard intervals G2 and G3 may be included in the HEW SIG-A field.

In uplink MU-MIMO transmission, multiple STAs may apply a beamformingmechanism to their transmission PPDUs. Information indicating whetherbeamforming is applied may be included in an HEW SIG-A field and/or anHEW SIG-B field. In an aspect, if the information indicating whetherbeamforming is applied is included in the HEW SIG-A, all STAs shouldperform beamforming application in unison. In this case, a samebeamforming mechanism (e.g., a beamforming steering matrix) may beapplied to waveforms in the HEW-STFs, HEW-LTFs, HEW SIG-Bs, and PSDUs ofall PPDUs transmitted by the STAs in the uplink MU-MIMO transmission. Inan aspect, if the information indicating whether beamforming is appliedis included in the HEW SIG-B, each STA may perform beamformingdifferently. In this case, such information included in the HEW SIG-Bmay indicate whether one STA participating in the uplink MU-MIMOtransmission is to perform the beamforming mechanism. Each of the STAsparticipating in the uplink MU-MIMO transmission may apply thebeamforming steering matrix only to waveforms of the HEW-STF, HEW-LTF,HEW SIG-B, and PSDU of a PPDU that the station transmits, according tothe value of the corresponding field.

FIG. 21 illustrates another example in which STA1, STA2, STA3, and STA4simultaneously transmit uplink data frames to the AP. The descriptionfrom FIG. 20 generally applies to FIG. 21, with examples of differencesbetween FIG. 20 and FIG. 21 and other description provided herein forpurposes of clarity and simplicity.

In an aspect, the HEW-LTFs are transmitted such that the number ofHEW-LTFs is adjusted to be identical to the number of transmittablespatial streams designated by the AP even if the number of spatialstreams that are actually transmitted by each of STA1, STA2, STA3, andSTA4 is less than the number of transmittable spatial streams designatedby the AP. For instance, even if 2, 1, 1, and 1 spatial streams havebeen respectively used for actual PSDU transmission, the numbers ofHEW-LTFs to be transmitted by the STA1, STA2, STA3, and STA4 are 4, 2,1, and 1, respectively.

Even in uplink MU-MIMO transmission, when the starting times of PSDUtransmission are different from each other, a problem of misalignmentbetween OFDM symbols may arise. To solve this problem, the interval towhich the guard interval G2 of the HEW PPDU format is applied may befixed at HEW-STF and HEW-LTF. Depending on the implementation, theinterval to which the guard interval G2 is applied may be limited onlyto the HEW-STF. Further, depending on the implementation, the intervalmay be limited to the range above the HEW-STF. Furthermore, depending onthe implementation, the interval to which guard interval G2 is appliedmay be limited to 0. After the interval to which guard interval G2 isapplied, guard interval G3 may equally be applied to all terminals for 0or one or more HEW-LTFs, the HEW SIG-B, and the PSDU depending on theuplink MU-MIMO transmission vectors transmitted by the respectiveterminals. Depending on the implementation, the interval to which guardinterval G2 is applied may extend to the HEW SIG-B field. In this case,guard interval G2 may be used for some of the PSDUs transmitted by STA2,STA3, and STA4, and guard interval G3 is used for the remaining PSDUs.

In one or more aspects, an acknowledgement policy (Ack Policy) mechanismfor uplink MU-MIMO transmission may be utilized in an HEW PPDU.

FIG. 22 illustrates an example of a frame exchange sequence used foruplink MU-MIMO transmission. An AP may transmit an uplink MU-MIMO Pollframe to STAs granting/requesting uplink MU-MIMO transmission. In FIG.22, to request uplink MU-MIMO transmission to STA1, STA2, STA3, andSTA4, the AP may transmit an uplink MU-MIMO Poll frame to STA1, STA2,STA3, and STA4. The uplink MU-MIMO Poll frame directed to the STAs mayinclude a receiver address (e.g., address 1 field in the MAC Header) setto a broadcast address, a transmitter address (e.g., address 2 field inthe MAC Header) to a BSSID, and the AIDs of the STAs requesting uplinkMU-MIMO transmission in a payload.

In an aspect, upon receipt of the uplink MU-MIMO Poll frame, the STAsmay determine, based on the uplink MU-MIMO Poll frame, whether they arerequested to perform uplink MU-MIMO transmission. If the STAs aredestination STAs, they may transmit an uplink MU-MIMO PPDU to the APduring a time period indicated by the uplink MU-MIMO Poll frame. To makethe transmission times of the uplink MU-MIMO PPDU transmitted by theSTAs equal, MAC padding and PHY padding may be performed. In an aspect,MAC padding may refer to support of padding by aggregating 4 octets ofnull MPDUs in the form of an aggregated MPDU (A-MPDU) at the MAC layer.In an aspect, PHY padding may refer to filling a last OFDM symbol withbits. The number of bits added by PHY padding may be equal to or smallerthan 1 octet.

In FIG. 22, STA1 has DATA (e.g., HE-DATA) to be transmitted during atime period indicated by an uplink MU-MIMO Poll frame. Therefore, STA1may transmit an uplink MU-MIMO PPDU during the given time and thus maytransmit an uplink MU-MIMO PPDU during the given time without MACpadding. On the other hand, STA2, STA3, and STA4 may have no data to betransmitted during the time period indicated by the uplink MU-MIMO Pollframe and thus align their transmission times of the uplink MU-MIMO PPDUwith the transmission times of the uplink MU-MIMO PPDU of the other STAsby MAC padding. The Ack Policy of the MAC header of each uplink MU-MIMOPPDU may indicate Immediate Block ACK (e.g., the Ack Policy may be setto a value associated with Immediate Block ACK).

In an aspect, upon receipt of and in response to the uplink MU-MIMOPPDU, the AP may transmit block ACK frames to the STAs transmitting theuplink MU-MIMO PPDU. In an aspect, the AP may transmit an uplink MU-MIMOPoll frame requesting a next uplink MU-MIMO PPDU transmission along withthe Block ACK frames.

FIG. 23 illustrates an example of a frame exchange sequence used foruplink MU-MIMO transmission. In FIG. 23, STA1 may fail to receive anuplink MU-MIMO Poll frame. As illustrated in FIG. 23, there is nomeaningful DATA transmission in an uplink MU-MIMO PPDU transmitted onlyby STA2, STA3, and STA4. In this regard, MAC padding may degrade systemperformance in a situation where a STA (e.g., STA1 in FIG. 23) that hasa DATA frame enough to be transmitted during a time indicated by theuplink MU-MIMO Poll frame does not participate in the uplink MU-MIMOPPDU transmission.

In an aspect, to address such performance degradation caused by MACpadding, the Ack Policy of an uplink MU-MIMO PPDU may be set to DelayedBlock ACK and a different uplink MU-MIMO PPDU transmission time may beset for each transmitting STA.

In an aspect, upon receipt of an uplink MU-MIMO Poll frame, STAs maydetermine, based on the uplink MU-MIMO Poll frame, whether they arerequested to perform an uplink MU-MIMO transmission. If the STAs aredestination STAs, they may transmit an uplink MU-MIMO PPDU to the APduring a time period given/indicated by the uplink MU-MIMO Poll frame.The transmission times of the uplink MU-MIMO PPDU for the STAs may bedifferent, given that their respective transmission times do not exceedthe time given/indicated by the uplink MU-MIMO Poll frame. In an aspectof such a case, MAC padding is not necessary for an uplink MU-MIMO PPDUtransmission and only PHY padding is utilized (e.g., to fill a last OFDMsymbol with bits at the PHY layer).

In an aspect, the AP, which has transmitted the uplink MU-MIMO Pollframe, may activate an uplink MU-MIMO Poll timer as an error recoveryprocedure for an uplink MU-MIMO Poll procedure. If aPHY-RXSTART.indication primitive is not invoked during an uplink MU-MIMOPoll timeout after transmission of the uplink MU-MIMO Poll frame, the APmay perform a recovery procedure, since an error may have occurred inthe uplink MU-MIMO Poll procedure. On the other hand, if thePHY-RXSTART.indication primitive is invoked, the AP may consider (e.g.,assume) that at least one of the STAs requested for uplink MU-MIMO PPDUtransmission has started to transmit an uplink MU-MIMO PPDU. In thesituation that different uplink MU-MIMO PPDU transmission times are setfor different STAs, the AP may use the invocation of thePHY-RXEND.indication primitive in determining termination of the uplinkMU-MIMO PPDU transmission. The AP may then transmit a Block ACK to theSTAs in response to the received uplink MU-MIMO PPDU after an SIFS fromthe invocation time of the PHY-RXEND.indication primitive. ThePHY-RXSTART.indication primitive and PHY-RXEND.indication primitive aredescribed later in the present disclosure.

FIG. 24 illustrates an example of a frame exchange sequence between anAP and multiple stations. In FIG. 24, the PHY-RXSTART.indicationprimitive and the PHY-RXEND.indication primitive may be invoked as onlyone primitive without distinction made between transmitting STAs fromthe PHY layer to the MAC layer. In some cases, thePHY-RXSTART.indication primitive and the PHY-RXEND.indication primitivemay be individually invoked for individual uplink MU-MIMO PPDUstransmitted by the STAs, depending on implementation. In these cases,the time at which the PHY-RXEND.indication primitive may be invoked fromall STAs of the uplink MU-MIMO PPDU (that the AP is receiving duringdetermination of the completion of the uplink MU-MIMO PPDU transmission)becomes the ending time of the transmission and the uplink MU-MIMO PPDUreception.

In an aspect, if each STA has a different uplink MU-MIMO PPDUtransmission time, neither the STAs requested for the uplink MU-MIMOPPDU transmission (e.g., via the uplink MU-MIMO Poll frame) nor the APhave prior knowledge about when the uplink MU-MIMO PPDU is completelytransmitted. In such an aspect, each STA does not expect any immediatecontrol response after transmitting an uplink MU-MIMO PPDU, and a timerand timeout procedure for a control response frame are not defined. Asillustrated in FIG. 24, each STA may set the Ack Policy of the uplinkMU-MIMO PPDU to Delayed Block ACK, instead of Immediate Block ACK.

FIG. 25 illustrates an example of a recovery procedure of the uplinkMU-MIMO Poll procedure. In an aspect, in FIG. 25, thePHY-RXSTART.indication primitive is not invoked during an uplink MU-MIMOPoll timeout after transmitting an uplink MU-MIMO Poll frame. After theuplink MU-MIMO Poll timeout, the AP may determine the clear channelassessment (CCA) state of a channel during a PIFS. If the channel isidle, the AP may transmit an uplink MU-MIMO Poll frame again to theSTAs.

In an aspect, the partial association identifier (AID) is a non-uniqueSTA identifier that may be defined as shown in the table below. Thepartial_AID may be carried in the TXVECTOR parameter PARTIAL_AID of anHEW single user (SU) PPDU. In an aspect, the partial AID may be limitedto 9 bits. For instance, the partial AID may include a portion (e.g., 9bits) of a basic service set identifier (BSSID) or a portion of areceiver address (RA).

Condition GROUP_ID PARTIAL_AID Addressed to AP 0 BSSID[39:47] Addressedto Mesh STA 0 RA[39:47] Sent by an AP and 63 (dec(AID[0:8]) + addressedto a STA dec(BSSID[44:47] ⊕ associated with that AP BSSID[40:43]) × 2⁵)mod 2⁹ or where sent by a DLS or TDLS   ⊕ is a bitwise exclusive STA ina direct path to a   OR operation DLS or TDLS peer STA   mod X indicatesthe X-   modulo operation   dec(A[b:c]) is the   cast to decimaloperator where b is scaled by 2⁰ and c by 2^(c−b) Otherwise (see NOTE)63 0 NOTE The last row covers the following cases: A PPDU sent by anIBSS STA A PPDU sent by an AP to a non associated STA Any othercondition not explicitly listed elsewhere in the table

In an aspect, a STA transmitting an HEW SU PPDU carrying one or moregroup addressed MPDUs or transmitting an HEW non-data packet (NDP)intended for multiple recipients shall set the TXVECTOR parametersGROUP_ID to 63 and PARTIAL_AID to 0. In an aspect, a STA transmitting anHEW SU PPDU carrying one or more individually addressed MPDUs or an HEWNDP intended for a single recipient sets the TXVECTOR parametersGROUP_ID and PARTIAL_AID associated with a group ID and a partial AID,respectively, as shown in the table above.

In an aspect, in the above table:

AID[b:c] represents bits b to c inclusive of the AID of the recipientSTA with bit 0 being the first transmitted.

BSSID[b:c] represents bits b to c inclusive of the BSSID, with bit 0being the Individual/Group bit. In this representation, theIndividual/Group bit is BSSID[0] and BSSID[47] is the last transmittedbit.

RA[b:c] represents bits b to c inclusive of the RA field, with bit 0being the Individual/Group bit. In this representation, theIndividual/Group bit is RA[0] and RA[47] is the last transmitted bit.

In an aspect, a STA shall include the values computed in the above tablein the PHYCONFIG_VECTOR parameters PARTIAL_AID_LIST_GID00 andPARTIAL_AID_LIST_GID63. In an aspect, a STA that transmits an HEW PPDUto a direct link setup (DLS) or tunneled direct link setup (TDLS) peerSTA obtains the AID for the peer STA from the DLS Setup Request, DLSSetup Response, TDLS Setup Request, or TDLS Setup Response frame.

In an aspect, an AP should not assign an AID to a STA that results in a0 value PARTIAL_AID. In an aspect, a STA transmitting an HEW MU PPDUsets the TXVECTOR parameter GROUP_ID as described in the followingprocedure.

In an aspect, a value in the Group ID field in HEW-SIG-B in the range 1to 62 indicates an HEW MU PPDU. Prior to transmitting an HEW MU PPDU,group assignments have been established by the AP for DL-MU-MIMO capableSTAs using the Group ID Management frame. An example of a Group IDManagement frame format is provided in the table below.

Order Information 1 Category 2 VHT Action 3 Membership Status Array (seeMembership Status Array field) 4 User Position Array (see User PositionArray field)

FIG. 26 illustrates an example of a Membership Status Array fieldformat. In an aspect, the Membership Status Array field may be formed of8 octets. Within the Membership Status Array field, a 1-bit MembershipStatus sub-field for each group ID is set as follows:

Set to 0 if the STA is not a member of the group;

Set to 1 if the STA is a member of the group.

FIG. 27 illustrates an example of a User Position Array field format. Inan aspect, the User Position Array field may be formed of 16 octets. TheUser Position Array field may be indexed by a group ID. The UserPosition Array field (indexed by the group ID) may include a 2-bit UserPosition sub-field for each of 64 group IDs. In some cases, after aSTA's MAC layer management entity (MLME) is configured using thePHYCONFIG_VECTOR parameter GROUP_ID_MANAGEMENT, the following lookuptables may be populated:

a) group ID to Membership Status, denoted byMembershipStatusInGroupID[g] for 1<=g<=62;

b) group ID to User Position, denoted by UserPositionlnGroupID[g] for1<=g<=62.

In an aspect, when a STA receives an HEW MU PPDU where the Group IDfield in the HEW-SIG-B field has a value k and whereMembershipStatusInGroupID[k] is equal to 1, the number of space-timestreams for that STA may be indicated in theMU[UserPositionInGroupID[k]] NSTS field in the HEW-SIG-B field. Thespace-time streams of different users may be ordered in accordance withuser position values (e.g., the space-time streams for the user in userposition 0 come first, followed by the space-time streams for the userin position 1, followed by the space-time streams for the user inposition 2, followed by the space-time streams for the user in position3, etc.).

In an aspect, a STA may be able to identify the space-time streamsintended for other STAs that act as interference. For instance, HEW-LTFsymbols in the HEW MU PPDU may be used to measure the channel for thespace-time streams intended for the STA and can also be used to measurethe channel for the interfering space-time streams. To successfullydemodulate the space-time streams intended for the STA, the STA may usethe channel state information for all space-time streams to reduce theeffect of interfering space-time streams. In some cases, if a STAdetermines that it is not a member of the group, or the STA is a memberof the group but the corresponding MU NSTS field in the HEW-SIG-B fieldindicates that there are zero space-time streams for the STA in thePPDU, the STA may elect to not process the remainder of the PPDU.

FIG. 28 illustrates an example of a frame exchange sequence between anAP and multiple stations. In an aspect, the downlink (DL) and uplink(UL) frame exchange sequence may be performed using an OFDMA mechanism.

First, the AP may transmit a DL OFDMA PPDU in an HE PPDU format, denotedas Downlink HE OFDMA PPDU in FIG. 28. The HE PPDU format is composed ofthe legacy preamble (e.g., using 64 FFT over 20 MHz channel), the HEpreamble (e.g., using 256 FFT over 20 MHz channel) and the PSDU. ThePSDU of the DL HE OFDMA PPDU has DATA (e.g., HE-DATA fields) formultiple STAs, including STA1, STA2, STA3, STA4, STA5, STA6, and STAT.The AP may transmit the DATA to these stations through sub-channels of 5MHz, 5 MHz, 10 MHz, 5 MHz, 5 MHz, 5 MHz, and 5 MHz, respectively. Afterthe SIFS from receiving the DL HE OFDMA PPDU, STA1 and STA4 may transmitcontrol response frames with (e.g., as part of) the UL OFDMA PPDU in theHE PPDU format, denoted as Uplink HE OFDMA PPDU in FIG. 28.

FIG. 29 illustrates another example of a frame exchange sequence betweenan AP and multiple stations. The description from FIG. 28 generallyapplies to FIG. 29, with examples of differences between FIG. 28 andFIG. 29 and other description provided herein for purposes of clarityand simplicity. In an aspect, the downlink (DL) and uplink (UL) frameexchange sequence may be performed using an OFDMA mechanism. In anaspect, after the SIFS from receiving the DL OFDMA PPDU, STA1 and STA4may transmit control response frames with UL OFDMA PPDU in a non-HT PPDUformat.

In an aspect, the control response frames transmitted in the UL OFDMAand UL MU-MIMO may use the same PPDU format (e.g., HE PPDU format ornon-HT PPDU format). In some cases, a control response frame may becarried in an HE PPDU format as shown in FIG. 28 if an eliciting framecarried in the HE PPDU format contains sub-channel assignmentinformation for each control response frame. In other cases, a controlresponse frame may be carried in a non-HT PPDU format as shown in FIG.29. In an aspect, the AP can explicitly indicate the PPDU type (e.g., HEPPDU format and non-HT PPDU format) of the control response frame in theframe eliciting response.

A first way to indicate the PPDU type may be to include that informationin the High Efficiency (HE) Control field in the MAC header. A secondway to indicate the PPDU type may be to include that information in theSIG field in the PHY header. The recipient STAs of the DL OFDMA PPDUcontaining the PPDU type information of the control response frame maytransmit the control response frame in the PPDU format specified by thePPDU type information explicitly signalled in the DL OFDMA PPDU. It isnoted that the other STAs that support the OFDM PPDU (e.g., IEEE802.11a/g/n/ac/ax STA) and receive the control response frame carried inthe non-HT PPDU format can update their respective Network AllocationVector (NAV).

In an aspect, the control response frames transmitted in the UL OFDMAand UL MU-MIMO shall have the transmitter address (TA) field forclarifying the transmitting STA of the control response frames. In thatsense, an HE acknowledgement (ACK) frame or a Block Ack frame may beused on behalf of (e.g., in place of) an ACK frame. In an aspect, when acontrol response frame is an A-MPDU format transmitted in the UL OFDMAand UL MU-MIMO, the A-MPDU shall carry at least one MPDU containing theTA field.

FIG. 30 illustrates an example of an HE acknowledgement (ACK) frame. TheHE ACK frame may be 20 octets. The HE ACK frame may include a framecontrol field, a duration field, a receiver address (RA) field, atransmitter address (TA) field, and a frame check sequence (FCS) field.

In an aspect, regarding a TXVECTOR parameter of a control response frametransmitted in the UL OFDMA and UL MU-MIMO, a STA shall set the TXVECTORparameter GI_TYPE of a control response frame carried in the HE PPDUformat to the RXVECTOR parameter GI_TYPE of a frame eliciting theresponse. Additionally, the STA shall set the TXVECTOR parameter GI_TYPEof a control response frame carried in the non-HT PPDU format to theLONG_GI (0.8 μs).

While receiving control response frames transmitted in a UL OFDMA PPDUor a UL MU-MIMO PPDU, the AP may transfer a payload (e.g., DATA,HE-DATA) from a PHY to a local MAC entity with the belowPHY-DATA.indication primitive. The primitive provides the followingparameters:

PHY-DATA.indication(  DATA  USER_INDEX )

In an aspect, the DATA parameter may be an octet of value X′00′ toX′FF′. In an aspect, the USER_INDEX parameter (typically identified as ufor an HEW STA) may be present for a UL OFDMA PPDU or a UL MU-MIMO PPDUand may indicate the index of the user in the RXVECTOR to which theaccompanying DATA octet applies. Otherwise, this parameter is notpresent.

The PHY-DATA.indication primitive may be generated by a receiving PHYentity to transfer the received octet of data to the local MAC entity.The time between receipt of the last bit of the last provided octet fromthe wireless medium (WM) and the receipt of this primitive by the MACentity is aRxPHYDelay. In an aspect, the effect of receipt of thisprimitive by the MAC is unspecified.

In an aspect, the AP may determine a transmission failure of a DL OFDMAPPDU as follows:

After transmitting one or more MPDUs (e.g., A-MPDUs or HE single MPDUsas part of a DL OFDMA PPDU) that require one or more immediate responseframes from one or more STAs, the AP shall wait for a timeout intervalof duration of aSIFSTime+aSlotTime+aRxPHYStartDelay, starting at thePHY-TXEND.confirm primitive. If a PHYRXSTART.indication primitive doesnot occur during the timeout interval, the AP may conclude that thetransmission of the DL OFDMA PPDU has failed.

If a PHY-RXSTART.indication primitive does occur during the timeoutinterval, the AP shall wait for the corresponding PHY-RXEND.indicationprimitive to recognize one or more valid response frames sent by the oneor more recipient STAs of the DL OFDMA PPDU requiring one or moreresponse frames. The recognitions of the transmission failures of the DLOFDMA PPDU addressed to one or more recipient STAs are individuallydetermined for each recipient STAs requiring an individual immediateresponse frame. The transmission failure event of receiving no validresponse frames from one or more primary recipient STAs may beinterpreted as a failure of the DL OFDMA PPDU. The AP should invoke aback-off procedure after the failure of the DL OFDMA PPDU.

In an aspect, a primary recipient STA is a recipient STA of which thecontrol response frame occupies a primary channel. In an aspect, anon-primary recipient STA is a recipient STA of which the controlresponse frame occupies a non-primary channel.

Even if a valid response frame is received from a non-primary recipientSTA, the transmission of the DL OFDMA PPDU may be interpreted as afailure if the AP receives no valid response frame from a primaryrecipient STA.

In an aspect, an aggregate medium access control (MAC) protocol dataunit (A-MPDU) may be, or may be defined as, a structure that containsone or more MPDUs and is transported by a physical layer (PHY) as asingle PHY service data unit (PSDU).

In an aspect, a high efficiency (HE) single medium access control (MAC)protocol data unit (HE single MPDU) may be, or may be defined as, anMPDU that is the only MPDU in an aggregate MPDU (A-MPDU) carried in anHE physical layer (PHY) protocol data unit (PPDU) and that is carried inan A-MPDU subframe with the end of frame (EOF) sub-field of the MPDUdelimiter field equal to 1. In an aspect, the A-MPDU may include a dataframe and a control frame (e.g., trigger frame). In an aspect, theA-MPDU may include a trigger frame and any single MPDU.

In an aspect, a PHY-TXEND.confirm primitive is described as follows.This primitive may be issued by the PHY to the local MAC entity toconfirm the completion of a transmission. In an aspect, this primitivemay be issued by the PHY to the MAC entity when the symbol containingthe last data octet has been transferred and any Signal Extension hasexpired. In an aspect, the receipt of this primitive by the MAC entitymay provide the time reference for the contention backoff protocol. Inan aspect, this primitive does not have any parameters.

In an aspect, the PHYRXSTART.indication primitive is described asfollows. This primitive may be an indication by the PHY to the local MACentity that the PHY has received a valid start of a PPDU, including avalid PHY header. The primitive may provide the following parameter:

PHY-RXSTART.indication(  RXVECTOR )

In an aspect, the RXVECTOR represents a list of parameters that the PHYprovides the local MAC entity upon receipt of a valid PHY header or uponreceipt of the last PSDU data bit in the received frame.

This primitive may be generated by the local PHY entity to the MACsublayer when the PHY has successfully validated the PHY header at thestart of a new PPDU. After generating a PHY-RXSTART.indicationprimitive, the PHY may be expected to maintain physical medium busystatus during the period required by that PHY to transfer a frame of anindicated LENGTH at an indicated DATARATE. In an aspect, this physicalmedium busy condition should be maintained even if aPHY-RXEND.indication(CarrierLost) primitive or aPHYRXEND.indication(FormatViolation) primitive is generated by the PHYprior to the end of this period.

In an aspect, the PHY-RXEND.indication primitive is described asfollows. The PHY-RXEND.indication may be an indication by the PHY to thelocal MAC entity that the PSDU currently being received is complete. Theprimitive may provide the following parameters:

PHY-RXEND.indication(  RXERROR,  RXVECTOR )

In an aspect, the RXERROR parameter can convey one or more of thefollowing values: NoError, FormatViolation, CarrierLost, orUnsupportedRate. In some cases, a number of error conditions may occurafter the PHY's receive state machine has detected what appears to be avalid preamble and state frame delimiter (SFD). The following describesthe parameter returned for each of those error conditions.

NoError. This value may be used to indicate that no error occurredduring the receive process in the PHY.

FormatViolation. This value may be used to indicate that the format ofthe received PPDU was in error.

CarrierLost. This value may be used to indicate that during thereception of the incoming PSDU, the carrier was lost and no furtherprocessing of the PSDU can be accomplished.

UnsupportedRate. This value may be used to indicate that during thereception of the incoming PPDU, a nonsupported date rate was detected.

Filtered. This value may be used to indicate that during the receptionof the PPDU, the PPDU was filtered out due to a condition set in thePHYCONFIG_VECTOR.

In an aspect, the RXVECTOR may represent a list of parameters that thePHY provides the local MAC entity upon receipt of a valid PHY header orupon receipt of the last PSDU data bit in the received frame.

In an aspect, the PHY-RXEND.indication primitive may be generated by thePHY for the local MAC entity to indicate that the received state machinehas completed a reception with or without errors. When a SignalExtension is present, the primitive may be generated at the end of theSignal Extension. In the case of an RXERROR value of NoError, the MACmay use the PHY-RXEND.indication primitive as reference for channelaccess timing.

In an aspect, the PHY-RXSTART.indication primitive and thePHY-RXEND.indication primitive may be invoked individually forindividual uplink MU-MIMO PPDUs transmitted by STAs depending onimplementation. In this case, when the PHY-RXEND.indication primitive isinvoked from all STAs of the uplink MU-MIMO PPDUs that the AP isreceiving, the AP may transmit a Block ACK to the STAs only when anRXERROR parameter of an uplink MU-MIMO PPDU received from at least oneSTA is set to NoError. In an aspect, the effect of receipt of thisprimitive is for the MAC to begin inter-frame space processing.

FIG. 31 illustrates an example of a channel list parameter for a 40 MHz,80 MHz, and 160 MHz channel width. In an aspect, a WLAN system maysupport a single channel having a bandwidth of 20 MHz as a basic serviceset (BSS) operating channel. The WLAN system may also support a BSSoperating channel having a bandwidth of 40 MHz, 80 MHz, or 160 MHz bybonding a plurality of contiguous 20-MHz channels. Further, the WLANsystem may support a BSS operating channel having a bandwidth of 160MHz, including non-contiguous 80-MHz channels (e.g., 80+80 MHz) notshown in FIG. 31.

As shown in FIG. 31, one 40-MHz channel may include a primary 20-MHzchannel and a secondary 20-MHz channel which are contiguous. One 80-MHzchannel may include a primary 40-MHz channel and a secondary 40-MHzchannel which are contiguous. One 160-MHz channel may include a primary80 MHz channel and a secondary 80-MHz channel which are contiguous.

A primary channel may be defined as a common channel of operation forall stations (STAs) that are members of the BSS. The primary channel maybe used for transmission of a basic signal such as a beacon. The primarychannel may also be a basic channel used for transmission of a data unit(e.g., a PPDU). If a STA uses a channel width larger than the channelwidth of the primary channel, for data transmission, the STA may useanother channel within a corresponding channel, in addition to theprimary channel. This additional channel is referred to as a secondarychannel.

In an aspect, in a UL OFDMA and a UL MU-MIMO, a STA may need to respondto an AP uplink start indication with a timing accuracy on the order of100 ns. In addition, the STA may need to correct uplink transmissionsfor frequency offset relative to the AP. For this purpose, the elicitingframe of a UL OFDMA and a UL MU-MIMO may be used as the reference frame.For example, in an aspect, in FIG. 28 and FIG. 29, because a Downlink HEOFDMA PPDU elicited the control response frames carried in the Uplink HEOFDMA PPDU, the Downlink HE OFDMA PPDU may be used as a reference framefor compensating the frequency offset relative to the AP. Afterreceiving the Downlink HE OFDMA PPDU, the STAs (e.g., STA1 and STA4)transmitting an elicited control response frame may adjust theirfrequency offset such that their adjusted frequency offset is identical(or substantially identical) with the frequency offset of the receivedDownlink HE OFDMA PPDU. In that sense, the STA may measure the frequencyoffset of the received frame and store the measured frequency offset ina dot11HighEfficiencyFrequency Offset MIB variable.

In an aspect, an enhancement of the accuracy of the frequency offsetcompensation may allow enhancement of UL OFDMA and/or UL MU-MIMOperformance. For example, when a UL OFDMA or a UL MU-MIMO PPDU istransmitted in 256 FFT, the reference frame should be transmitted in 256FFT. Otherwise, if a UL OFDMA or a UL MU-MIMO PPDU compensates itsfrequency offset from a more coarse granularity signal transmitted in 64FFT, the frequency offset difference between multiple uplinktransmissions may adversely affect performance.

In an aspect, a UL OFDMA and/or a UL MU-MIMO can be initiated byreceiving a polling frame from the AP. FIG. 32 illustrates an example ofan exchange of frames between an AP and multiple stations. In an aspect,the exchange of frames may be associated with a UL MU polling procedure.

First, the AP may transmit an uplink MU-MIMO Poll frame to one or moregranted STAs of uplink MU-MIMO PPDU transmissions. The uplink MU-MIMOPoll frame may be (and, in FIG. 32, is denoted as) a non-HT PPDU. Thegranted STAs may be included in an Uplink Multi-User Polled STA field ofthe uplink MU-MIMO Poll frame. After receiving the uplink MU-MIMO Pollframe, the granted STAs may transmit uplink MU-MIMO PPDUs at an SIFSafter receiving the uplink MU-MIMO Poll frame. As shown in FIG. 32, theuplink MU-MIMO PPDUs are, or are included as part of, an HE PPDU. Then,the AP may transmit a Block ACK frame containing an acknowledgementstatus of the uplink MU-MIMO PPDUs transmitted from the granted STAs. Inan aspect, the uplink MU-MIMO Poll frame, uplink MU-MIMO PPDUs, andBlock ACK frame may be transmitted in 64 FFT, 256 FFT, and 64 FFT,respectively.

As previously mentioned, in an aspect, an enhancement of the accuracy ofthe frequency offset compensation may allow enhancement of UL OFDMAand/or UL MU-MIMO performance. In FIG. 32, the UL MU-MIMO PPDUs istransmitted in 256 FFT but the uplink MU-MIMO Poll frame (which can beconsidered a reference frame) is transmitted in 64 FFT. In such a case,a frequency offset inaccuracy may adversely affect performance.

In an aspect, 256 FFT may be utilized for the reference signal. FIG. 33illustrates an example of an exchange of frames between an AP andmultiple stations. The description from FIG. 32 generally applies toFIG. 33, with examples of differences between FIG. 32 and FIG. 33 andother description provided herein for purposes of clarity andsimplicity.

First, the AP may transmit an uplink MU-MIMO Poll frame to one or moregranted STAs of uplink MU-MIMO PPDU transmissions. Rather than a non-HTPPDU of 64 FFT, an HE PPDU of 256 FFT may be used for the uplink MU-MIMOPoll frame. After receiving the uplink MU-MIMO Poll frame, the grantedSTAs may transmit uplink MU-MIMO PPDUs at an SIFS after receiving theuplink MU-MIMO Poll frame. Because the uplink MU-MIMO Poll frametransmitted in 256 FFT (e.g., a finer granularity signal compared tobeing transmitted in 64 FFT) is used as the reference signal, theperformance of the uplink MU-MIMO can be enhanced. Then, the AP maytransmit a Block ACK frame containing an acknowledgement status of theuplink MU-MIMO PPDUs transmitted from the granted STAs. In an aspect,the Block ACK frame may be (and, in FIG. 33, is denoted as) an HE PPDU.

In an aspect, by using 256 FFT for the reference signal, the performanceof the uplink MU-MIMO can be enhanced. An issue may be that a legacy STAcannot decode the reference signal that is an uplink MU-MIMO Poll framewhen the uplink MU-MIMO Poll frame is transmitted in 256 FFT. In such acase, protection performance may be degraded because the legacy STAcannot set the NAV for the follow-up uplink MU-MIMO PPDU.

In an aspect, a manner by which to address this issue may be to use anon-HT PPDU of 64 FFT for the reference signal. In order to providefiner granularity for the frequency offset compensation, an additionalsignal of 256 FFT can be appended after the non-HT PPDU referencesignal. FIG. 34 illustrates an example of an exchange of frames betweenan AP and multiple stations. The description from FIG. 32 generallyapplies to FIG. 34, with examples of differences between FIG. 32 andFIG. 34 and other description provided herein for purposes of clarityand simplicity.

First, the AP may transmit an uplink MU-MIMO Poll frame to one or moregranted STAs of uplink MU-MIMO PPDU transmissions. The uplink MU-MIMOPoll frame may be a non-HT PPDU of 64 FFT and may be used for thereference signal. In order to enhance granularity of the frequencyoffset compensation, an additional signal of 256 FFT is appended after(e.g., immediately after) the non-HT PPDU. In FIG. 34, the additionalsignal is an HE-LTF field. After receiving the uplink MU-MIMO Pollframe, the granted STAs may transmit uplink MU-MIMO PPDUs SIFS (e.g., atthe end of SIFS) after receiving the uplink MU-MIMO Poll frame. In anaspect, because the finer granularity signal transmitted in 256 FFT isappended to the reference signal, the performance of the uplink MU-MIMOcan be enhanced by compensating the frequency offset based on theappended signal of 256 FFT. Also, because the legacy STA can decode thereference signal, the protection performance can be enhanced. Then, theAP may transmit a Block ACK frame containing an acknowledgement statusof the uplink MU-MIMO PPDUs transmitted from the granted STAs. Theuplink MU-MIMO Poll frame may be (and, in FIG. 34, is denoted as) anon-HT PPDU. In an aspect, the Block ACK frame may be transmitted in 64FFT.

In an aspect, an uplink MU-MIMO Poll frame may contain a list of grantedSTAs, a list of a number of space-time streams, and a list of frequencyallocations for uplink MU-MIMO PPDU transmissions. The uplink MU-MIMOPoll frame may also contain Traffic Identifier (TID) and/or AccessCategory (AC) information for uplink MU-MIMO PPDU transmissions. In someaspects, the ACs may include a voice (VO) access category, a video (VI)access category, a best effort (BE) access category, and a background(BK) access category, denoted as AC-VO, AC-VI, AC-BE, and AC-BK,respectively. In an aspect, the ACs may be in order of priority, fromhighest to lowest priority: AC-VO, AC-VI, AC-BE, and AC-BK. In anaspect, when the TID or AC information for uplink MU-MIMO PPDUtransmissions is not contained in the uplink MU-MIMO Poll frame, anyMSDU, regardless of its TID or AC, can be transmitted in the uplinkMU-MIMO PPDU. Otherwise, in this aspect, when the TID and/or ACinformation is contained, only MSDUs matched with the TID and/or ACspecified in the iplink MU-MIMO Poll frame can be transmitted in theuplink MU-MIMO PPDU.

After receiving the uplink MU-MIMO PPDU(s) transmitted from the grantedSTA(s), the AP may transmit a Block ACK frame containing anacknowledgement status of the corresponding uplink MU-MIMO PPDU(s).

FIG. 35 illustrates an example of a Block ACK (BA) frame format. In anaspect, the Block ACK frame may be transmitted by the AP in a DL MU PPDU(e.g., as a broadcast frame) in response to received uplink MU-MIMOPPDU(s) from the granted STAs. The Block ACK frame may include a framecontrol field, a duration/ID field, an RA field, a TA field, a Per-UserACK fields, and an FCS field. In FIG. 35, a first, second, and thirdPer-User ACK field may be for STA1, STA2, and STA3, respectively. In anaspect, a Per-User ACK field may be referred to as a Per StationInformation (Per STA Info) field. It is noted that the ellipses betweenthe third Per-User ACK field and the FCS field indicate that one or moreadditional Per-User ACK fields or no Per-User ACK field are presentbetween the third Per-User ACK field and the FCS field.

In an aspect, each Per-User ACK field may represent acknowledgementinformation for a respective AID and TID associated with the thereceived uplink MU-MIMO PPDUs. In this regard, a Per-User ACK field mayrepresent acknowledgement information of an uplink MU-MIMO PPDU (amongthe uplink MU-MIMO PPDUs from the granted STAs) that is identified withor otherwise associated with the respective AID and TID. In an aspect,the partial AID may indicate a STA's local address.

Each Per-User ACK field may include an Ack Policy sub-field, an AIDsub-field, and a TID sub-field. In an aspect, the Ack Policy sub-field,AID sub-field, and TID sub-field may be 1 bit, 11 bits, and 4 bits,respectively. In an aspect, the term sub-field may be referred to as afield, and/or vice versa. In an aspect, the Ack Policy sub-field may bereferred to as an Ack Type sub-field. In an aspect, the Ack Policysub-field, AID sub-field, and TID sub-field form a Per AID TIDInformation (Per AID TID Info) sub-field. Thus, in this aspect, thePer-User ACK field includes the Per AID TID Info sub-field. The AIDsub-field in the Per-User ACK field may be set to the AID of the grantedSTA from which the AP receives the uplink MU-MIMO PPDU. It is noted thatin infrastructure BSS operation, the AID sub-field may contain a valueassigned by an AP during association. In some cases, the AID sub-fieldmay represent a 16-bit ID of a STA.

In an aspect, the TID sub-field in the Per-User ACK field may be set tothe TID or AC of the uplink MU-MIMO PPDU received from the granted STAthat is specified in the AID sub-field. In some cases, when there is noBlock ACK agreement (e.g., Per-User ACK field represents the ACK), theTID sub-field may be reserved (e.g., set) to 0.

In an aspect, when the Ack Policy sub-field of the Per-User ACK field isequal to a first value (e.g., 1), a Block Acknowledgement (BA) Controlfield and a BA Information field may be present in the Per-User ACKfield. In an aspect, when the Ack Policy sub-field is equal to a secondvalue (e.g., 0), the BA Control and BA Information fields are notpresent in the Per-User ACK field. In an aspect, the BA Control and BAInformation sub-fields may have a Block ACK bitmap and Block AckStarting Sequence Control. In an aspect, the BA Information sub-fieldincludes a Block Ack Starting Sequence Control sub-field and a Block AckBitmap sub-field. Thus, in this aspect, when the Ack Policy sub-field isequal to the first value, the Block Ack Starting Sequence Control andBlock Ack bitmap are present in the Per-User ACK field, and when the AckPolicy sub-field is equal to the second value, the Block Ack StartingSequence Control and Block Ack bitmap are not present in the Per-UserACK field. The Ack Policy sub-field being equal to the second value mayindicate an ACK of either a single MPDU or all MPDUs carried in theeliciting PPDU that was transmitted by the STA whose AID is indicated inthe AID sub-field of the Per-User ACK field. In the foregoing, the firstvalue and second value are 1 and 0, respectively, by way of non-limitingexample. In other words, in some aspects, the first value may be 0 andthe second value may be 1.

In an aspect, when the TID or AC information for the uplink MU-MIMO PPDUtransmissions is contained in the uplink MU-MIMO Poll frame, the TIDsub-field in the Per-User ACK field (for acknowledging the uplinkMU-MIMO PPDUs) may be set to the same TID or AC information indicated inthe uplink MU-MIMO Poll frame. In an aspect, when the TID or ACinformation for the uplink MU-MIMO PPDU transmissions is not containedin the uplink MU-MIMO Poll frame, the TID sub-field in the Per-User ACKfield may be set to the TID or AC of the received uplink MU-MIMO PPDU.

The Per-User ACK fields are listed for each AID. For example, when theAP receives MPDUs having different TIDs from a single granted STA, theBlock ACK frame may include multiple Per-User ACK fields for the singlegranted STA. In such a case, a first instance of the Per-User ACK fieldshaving the same AID may correspond to a lowest TID value, withsubsequent instances ordered by increasing value of the TID field.

In an aspect, the AP can determine one or more target poll transmissiontimes (TPTTs). In a TPTT, the AP shall schedule an uplink MU-MIMO Pollframe (or uplink OFDMA Poll frame) transmission. In some cases, a TPTTinformation element may be included in a beacon frame. In such cases, aSTA that receives a beacon frame with a TPTT information element maylisten for the uplink MU-MIMO Poll frame (or uplink OFDMA Poll frame)transmitted at the TPTT. In an aspect, an uplink multi-user poll framemay refer to an uplink MU-MIMO Poll frame or an uplink OFDMA Poll frame.In an aspect, description pertaining to an uplink MU-MIMO Poll frame mayalso apply to an uplink OFDMA Poll frame, and/or vice versa.

In some cases, an uplink MU-MIMO Poll frame (or uplink OFDMA Poll frame)can be used for an anonymous user. In such cases, the uplink MU-MIMOPoll frame (or uplink OFDMA Poll frame) may have an empty list of thegranted STAs. In order to choose the group of candidate STAs amonganonymous users, the uplink MU-MIMO Poll frame (or uplink OFDMA Pollframe) may have a condition(s) associated with participating in anuplink MU-MIMO transmission or an uplink OFDMA transmission.

In an aspect, each STA performing an enhanced distributed channel access(EDCA) may suspend an operation of its enhanced distributed channelaccess function (EDCAF) at the TPTT or at a reception time of an uplinkMU-MIMO Poll frame (or uplink OFDMA Poll frame), and may store the valueof a backoff counter, CW[AC], QSRC[AC], and QLRC[AC]. In an aspect, CW,QSRC, and QLRC denote contention window, QoS long retry counter, and QoSshort retry counter, respectively, and their values may be dependent onthe access category. At an end of a transmission opportunity (TXOP)controlled by an uplink MU-MIMO Poll frame (or uplink OFDMA Poll frame),the stored backoff function state may be restored and an operation ofthe EDCAF may be resumed. In an aspect, if the previously stored backofffunction state is empty, the EDCAF of a STA may invoke a backoffprocedure, even if no additional transmissions are currently queued.

In some aspects, if traffic load is not heavy, after a successfultransmission of an uplink MU-MIMO PPDU or an uplink OFDMA PPDU, each STAperforming an EDCA access may reset a backoff counter, CW[AC], QSRC[AC],and QLRC[AC] (e.g., on behalf of unchanging its backoff function state).If the traffic load is heavy, after a transmission failure of an uplinkMU-MIMO PPDU or an uplink OFDMA PPDU, each STA performing an EDCA accessmay increment a backoff counter, CW[AC], QSRC[AC], and QLRC[AC], onbehalf of unchanging its backoff function state.

In an aspect, when one or more granted STAs transmit uplink MU-MIMOPPDUs, all PSDU transmission time (TXTIME) is identical. For thispurpose, MAC padding (e.g., null A-MPDU end of frame (EOF) padding)mechanism may be used. In an aspect, MAC padding may refer to support ofpadding by aggregating 4 octets of null MPDUs in the form of anaggregated MPDU (A-MPDU) at the MAC layer. In some cases, fragmentationof A-MPDU subframe can be used for increasing resource utilization.

FIG. 36 illustrates an example of an exchange of frames between an APand multiple stations. The exchange of frames may be associated with afragmentation mechanism of an A-MPDU subframe. In an aspect, when a lastA-MPDU subframe of an A-MPDU causes a TXTIME of the A-MPDU to exceed agranted TXTIME for a multi-user PPDU, the last A-MPDU subframe of theA-MPDU can be fragmented into two parts. For example, in FIG. 36, thelast A-MPDU subframe of the PSDU addressed to STA1 is fragmented intotwo parts, denoted as “A-MPDU Subframe3 (Split field set to 1)” and“A-MPDU Subframel (Split field set to 1)” because a TXTIME of the A-MPDUwould exceed the granted TXTIME without the fragmentation. These twoparts may be referred to as a first fragmented A-MPDU subframe and asecond fragmented A-MPDU subframe. In an aspect, the first and secondfragmented A-MPDU subframes may be consecutively transmitted with animmediate acknowledgement. In this regard, multi-user PPDUs, includingthe fragmented MPDUs (e.g., fragmented A-MPDU subframes), may beconsecutively transmitted with an immediate acknowledgement in an SIFSinterval, as the following:

[Multi-User PPDU including the fragmented MPDU]+SIFS+[AcknowledgementPPDU]+SIFS+[Multi-User PPDUs including the fragmentedMPDU]+SIFS+[Acknowledgement PPDU]

In some cases, a multi-user PPDU exchange sequence, including thefragmented MPDU (e.g., fragmented A-MPDU subframe), may be limited to asingle TXOP. In these cases, when all fragmented MPDUs are not exchangedwithin a single TXOP, the multi-user PPDU exchange sequence does notinclude any fragmented MPDU.

In some cases, multiple fragmented MPDUs of the same MPDU cannot betransmitted together in a single HE PPDU. For instance, multiplefragmented A-MPDU subframes of the same A-MPDU subframe cannot betransmitted together in a single HE PPDU. On the other hand, fragmentedA-MPDU subframes of different A-MPDU subframes can be transmittedtogether in a single HE PPDU.

In an aspect, in order to support the fragmentation of an A-MPDUsubframe, an MPDU delimiter field in A-MPDU subframe may have afragmentation sub-field. The fragmentation sub-field may be set to 1when the corresponding A-MPDU subframe is fragmented. The fragmentationsub-field may be set to 0 when the corresponding A-MPDU subframe is notfragmented.

In an aspect, in the fragmentation of an A-MPDU subframe, afterreceiving an A-MPDU subframe with the fragmentation sub-field equal to1, if a STA does not successfully receive the immediately following(e.g., within a single TXOP) A-MPDU subframe with the fragmentationsub-field equal to 1, the STA may discard that fragmented A-MDPUsubframe. Else if a STA successfully receives the immediately following(e.g., within a single TXOP) A-MPDU subframe with the fragmentationsub-field equal to 1, the AP may merge the two fragmented A-MPDUsubframes.

In an aspect, when a STA determines that a medium is idle followingreception of a frame for which the PHY-RXEND.indication primitivecontained an error or a frame for which the MAC FCS value was notcorrect, a channel access mechanism of a STA may use an extended interframe space (EIFS) for distributed coordination function (DCF) or theEIFS-DIFS+AIFS[AC] interval for the EDCA before transmission.

The EIFS or EIFS-DIFS+AIFS[AC] interval may begin following anindication by the PHY that the medium is idle after detection of anerroneous frame, without regard to the virtual carrier sense (CS)mechanism. In an aspect, the STA does not begin a transmission until theexpiration of the later of the NAV and EIFS or EIFS-DIFS+AIFS[AC]. TheEIFS and EIFS-DIFS+AIFS[AC] may be defined to provide enough time foranother STA to acknowledge what was, to this STA, an incorrectlyreceived frame before this STA commences transmission. Reception of anerror-free frame during the EIFS or EIFS-DIFS+AIFS[AC] may resynchronizethe STA to the actual busy/idle state of the medium, so the EIFS orEIFS-DIFS+AIFS[AC] may be terminated and medium access (e.g., using DIFSor AIFS as appropriate and, if necessary, backoff) may continuefollowing reception of the error-free frame. At the expiration ortermination of the EIFS or EIFS-DIFS+AIFS[AC], the STA may revert to theNAV and physical CS to control access to the medium.

In an aspect, EIFS shall not be invoked if the NAV is updated by theframe that would have caused an EIFS, such as when the MAC FCS fails andthe L-SIG TXOP function employs L-SIG information to update the NAV. Inan aspect, EIFS shall not be invoked for an A-MPDU if one or more of itsframes are received correctly.

In an aspect, when dot11DynamicEIFSActivated is false or not defined,the EIFS is derived from the SIFS and the DIFS and the length of time ittakes to transmit an Ack frame at the lowest PHY mandatory rate may beprovided by the following equation.

EIFS=aSIFSTime+ACKTxTime+DIFS,

where ACKTxTime is the time (e.g., expressed in microseconds) requiredto transmit an Ack frame, including the preamble, PHY header, and anyadditional PHY dependent information, at the lowest PHY mandatory rate.

In an aspect, when dot11DynamicEIFSActivated is true, EIFS may be basedon an estimated duration of the PPDU that is a possible response to thePPDU that causes the EIFS. In an aspect, when dot11DynamicEIFSActivatedis true and the PPDU that causes the EIFS does not contain a single MPDUwith a length equal to a predetermined length (e.g., 14 or 32 octets),EIFS may be determined as shown in the following equation.

EIFS=aSIFSTime+EstimatedAckTxTime+DIFS,

where EstimatedAckTxTime may be based on an estimated duration of thePPDU that is a possible response to the PPDU that causes the EIFS, asspecified in the following table.

Other Modulation Rate/MCS of properties of Presumed of PPDU PPDU causingPPDU causing Presumed response EstimatedAck causing EIFS EIFS EIFSresponse rate TxTime (μs) (HR−)DSSS 1 Mbps Ack  1 Mbps 304 (HR−)DSSS ≥2Mbps (long Ack  2 Mbps 248 preamble) (HR−)DSSS ≥2 Mbps (short Ack  2Mbps 152 preamble) (ERP−)OFDM BPSK Ack  6 Mbps 44 (ERP−)OFDM QPSK Ack 12Mbps 32 (ERP−)OFDM ≥16-QAM Ack 24 Mbps 28 HT BPSK Aggregation = 0 Ack  6Mbps 44 HT QPSK Aggregation = 0 Ack 12 Mbps 32 HT ≥16-QAM Aggregation =0 Ack 24 Mbps 28 HT BPSK Aggregation = 1 BlockAck  6 Mbps 68 HT QPSKAggregation = 1 BlockAck 12 Mbps 44 HT ≥16-QAM Aggregation = 1 BlockAck24 Mbps 32

FIG. 37 illustrates an example of an exchange of frames between an APand multiple stations. In this regard, FIG. 37 shows an example of theAckTxTime for considering the EIFS. First, the AP may transmit a DLOFDMA PPDU in an HE PPDU format. The PSDU of the DL OFDMA PPDU may havethe DATA (e.g., HE-DATA) for multiple STAs, STA1, STA2, STA3, STA4,STA5, STA6, STA7 and STA8. The AP may transmit the DATA for these STAsthrough sub-channels of 2.5 MHz each. After an SIFS from receiving theDL OFDMA PPDU, STA1 may transmit control response frame with or as partof a UL OFDMA PPDU in the HE PPDU format. In an aspect, because a singlecontrol response frame occupies the 20 MHz channel, the AckTxTime isabout 68 μs.

FIG. 38 illustrates an example of an exchange of frames between an APand multiple stations. In this regard, FIG. 38 shows an example of theAckTxTime for considering the EIFS. First, the AP may transmit a DLOFDMA PPDU in an HE PPDU format. The PSDU of the DL OFDMA PPDU has theDATA (e.g., HE-DATA) for multiple STAs, STA1, STA2, STA3, STA4, STA5,STA6, STA7, and STA8. The AP may transmit the DATA for these stationsthrough sub-channels of 2.5 MHz each. After an SIFS from receiving theDL OFDMA PPDU, STA1, STA2, STA3, STA4, STA5, STA6, STA7, and STA8 mayeach transmit a control response frame with or as part of a UL OFDMAPPDU in the HE PPDU format. In an aspect, because the control responseframe from each STA occupies a 2.5 MHz channel, the AckTxTime may beabout 612 μs (e.g., increased from that shown in FIG. 37). As shown inFIGS. 37 and 38, according to the channel bandwidth of the controlresponse frame, the AckTxTime may vary from 68 μs to 612 μs.

In an aspect, after receiving an OFDMA HE PPDU, the EIFS of a thirdparty HE STA may be varied depending on a channel bandwidth of a controlresponse frame. In some cases, when the control response frame uses thesame channel bandwidth as the received OFDMA HE PPDU, the channelbandwidth of the control response frame can be implicitly determined bya sub-channel assignment structure of the received OFDMA HE PPDU.

In some cases, the HE preamble of the OFDMA HE PPDU may indicate thechannel bandwidth of the control response frame. When one or morecontrol response frames are simultaneously transmitted with differentchannel bandwidth, the minimum channel bandwidth of the control responseframes may be included in the HE preamble. Alternatively, in othercases, rather then indicating the channel bandwidth information of thecontrol response frame in the HE preamble, the HE preamble may includetransmission time information of the control response frame, which mayvary depending on the channel bandwidth of the control response frame.

In an aspect, when dot11DynamicEIFSActivated is true and the PPDU thatcauses the EIFS contains either a single MPDU of which the LENGTH fieldin L-SIG of the PHY header indicates a predetermined length (e.g., 14 or32 octets) or a VHT/HE single MPDU of which the MPDU Length field in theMPDU delimiter of the A-MPDU subframe indicates a predetermined length(e.g., 14 or 32 octets), the EIFS is equal to DIFS. In this aspect, thismay reflect the fact that an MPDU of the predetermined length (e.g., 14or 32 octet MPDU) is likely an Ack frame or a BlockAck frame, which doesnot cause a response PPDU to be transmitted.

In an aspect, a very high throughput (VHT)/High Efficiency (HE) singlemedium access control (MAC) protocol data unit (VHT/HE single MPDU) maybe an MPDU that is the only MPDU in an aggregate MPDU (A-MPDU) carriedin either a VHT physical layer (PHY) protocol data unit (PPDU) or an HEphysical layer (PHY) protocol data unit (PPDU) and that is carried in anA-MPDU subframe with the EOF sub-field of the MPDU delimiter field equalto 1.

In an aspect, the duration of a TXOP is the time a STA obtaining a TXOP(e.g., the TXOP holder) maintains uninterrupted control of the medium,and it includes the time required to transmit frames sent as animmediate response to transmissions by the TXOP holder.

In an aspect, the TXOP holder may be an HE AP. The TXOP holder shall nottransmit an uplink MU-MIMO Poll frame (or an uplink OFDMA Poll framewhen the follow-up uplink multi-user PPDU is an OFDMA), where the timerequired for the transmission of the uplink multi-user PPDUs and theassociated multi-user Block Ack frame plus two SIFSs exceeds the TXOPlimit. In an aspect, the uplink multi-user PPDU Duration field of atrigger frame that indicates the duration of the follow-up uplinkmulti-user PPDU transmission follows this constraint. The uplinkmulti-user PPDU Duration field (which indicates the time required forthe transmission of the uplink multi-user PPDUs and the associatedmulti-user Block Ack frame plus, e.g., two SIFSs) shall not exceed theTXOP limit. In other words, the value contained in the uplink multi-userPPDU Duration field shall not exceed the TXOP limit. In an aspect, aTXOP limit of 0 may indicate that the TXOP holder may transmit or causeto be transmitted (e.g., as responses) one of the following within thecurrent TXOP at any rate:

One or more SU PPDUs carrying fragments of a single MSDU or MACmanagement protocol data unit (MMPDU)

An SU PPDU or a VHT MU PPDU or an HE MU PPDU carrying a single MSDU, asingle MMPDU, a single A-MSDU, or a single A-MPDU

A VHT MU PPDU carrying A-MPDUs to different users (a single A-MPDU toeach user) or an HE MU PPDU carrying A-MPDUs to/from different users (asingle A-MPDU to/from each user)

A QoS Null frame or PS-Poll frame

In an aspect, the TXOP holder may exceed the TXOP limit only if it doesnot transmit more than one data or management frame in the TXOP, andonly for:

Retransmission of an MPDU, not in an A-MPDU consisting of more than oneMPDU

Initial transmission of an MSDU under a block acknowledgement agreement,where the MSDU is not in an A-MPDU consisting of more than one MPDU andthe MSDU is not in an A-MSDU

Transmission of an uplink multi-user Control MPDU or a QoS Null MPDU,not in an A-MPDU consisting of more than one MPDU

Initial transmission of a fragment of an MSDU or MMPDU, if a previousfragment of that MSDU or MMPDU was retransmitted

Transmission of a fragment of an MSDU or MMPDU fragmented into 16fragments

Transmission of an A-MPDU consisting of the initial transmission of asingle MPDU not containing an MSDU and that is not an individuallyaddressed management frame

Transmission of a group addressed MPDU, not in an A-MPDU consisting ofmore than one MPDU

Transmission of a Null Data Packet (NDP)

Transmission of a VHT NDP Announcement frame and NDP or transmission ofa Beamforming Report Poll frame that fits within the TXOP limit but theresponse and the immediately preceding SIFS cause the TXOP limit to beexceeded

FIG. 39 illustrates an example of an exchange of frames between an APand multiple stations. FIG. 39 shows an example of a valid TXOP limitrule for uplink multi-user data transmission. In an aspect, the frameexchange sequence including an uplink MU-MIMO Poll frame, uplink MU-MIMOPPDUs, and a Block ACK frame does not exceed the TXOP limit.

FIG. 40 illustrates an example of an exchange of frames between an APand multiple stations. FIG. 40 shows an example of an invalid TXOP limitrule for uplink multi-user data transmission. In this regard, the frameexchange sequence including an uplink MU-MIMO Poll frame, uplink MU-MIMOPPDUs, and a Block ACK frame exceeds the TXOP limit in FIG. 40. This isnot a valid frame exchange sequence for the uplink multi-usertransmission. Accordingly, in an aspect, the uplink MU-MIMO Poll framemay adjust the duration of the uplink MU-MIMO PPDU transmission to allowmeeting of the TXOP limit.

FIG. 41 illustrates an example of an exchange of frames between an APand multiple stations. FIG. 41 illustrates an example of a valid TXOPlimit rule for uplink multi-user ACK transmission. The frame exchangesequence of Downlink OFDMA Data frames and an Uplink OFDMA ACK frameexceeds the TXOP limit. Even though the frame exchange sequence exceedsthe TXOP limit, this is a valid frame exchange sequence because only thecontrol response frame (e.g., the Uplink OFDMA ACK frame) is exceedingthe TXOP limit.

In an aspect, when the UL OFDMA is used for multiplexing the BA/ACKresponse to the DL OFDMA PPDU and DL MU-MIMO PPDU, the sub-channelassignment information may be included in the DL OFDMA PPDU and DLMU-MIMO PPDU.

In an aspect, an A-MPDU may include the sub-channel assignmentinformation. A frame having the sub-channel assignment information maybe aggregated with other MPDUs and the frame transmitted to eachreceiver of the DL OFDMA PPDU and DL MU-MIMO PPDU. Alternatively or inaddition, in an aspect, a MAC header of the DL OFDMA PPDU and DL MU-MIMOPPDU has the sub-channel assignment information.

In an aspect, regarding an A-MPDU mechanism of the sub-channelassignment information, the following rules may be implemented. In somecases, at most one frame having the sub-channel assignment informationcan be included in the A-MPDU. The frame shall be the first or last MPDUin the A-MPDU. The Ack Policy of other QoS DATA MPDU in the A-MPDU shallnot be set to Normal Ack, Implicit Block Ack Request, or Block ACK. TheAck Policy behavior of receivers of the DL OFDMA PPDU and DL MU-MIMOPPDU should be differently interpreted according to the reception of theMPDU having the sub-channel assignment information in the DL OFDMA PPDUand DL MU-MIMO PPDU.

For example, the Ack Policy of the QoS DATA MPDU in the DL OFDMA PPDUand DL MU-MIMO PPDU may be set to a reserved value for indicating the ULOFDMA-based ACK. If the reserved value is set to 01, the Ack Policybehavior of receivers of the DL OFDMA and DL MU-MIMO PPDU can beprovided as follows:

Ack Policy set to 01: [PSMP context] or [UL OFDMA context]

In a frame that is the power save multi-poll (PSMP) context:

-   -   i) When bit 6 of the Frame Control field is set to 1:    -   There may be a response frame to the frame that is received, but        it is neither the Ack frame nor any data frame of        subtype+CF-Ack. The Ack Policy sub-field for QoS CF-Poll and QoS        CF-Ack+CF-Poll Data frames is set to this value.    -   ii) When bit 6 of the Frame Control field is set to 0:    -   The acknowledgement for a frame indicating PSMP Ack when it        appears in a PSMP downlink transmission time (PSMP-DTT) is to be        received in a later PSMP uplink transmission time (PSMP-UTT).        The acknowledgement for a frame indicating PSMP Ack when it        appears in a PSMP-UTT is to be received in a later PSMP-DTT.

In a frame that is the UL OFDMA context:

-   -   i) The addressed recipient that receives a frame having the        sub-channel assignment information returns an Ack/Block Ack        frame, either individually or as part of an A-MPDU starting a        SIFS after the PPDU carrying the frame, according to the        sub-channel assignment information specified in the received        frame.    -   ii) The addressed recipient that does not receive a frame having        the sub-channel assignment information takes no action upon the        receipt of the frame except for recording the state. The        recipient can expect a BlockAckReq frame in the future to which        it responds using the procedure described in a block        acknowledgement mechanism.

In an aspect, regarding an indication of the sub-channel assignmentinformation in the MAC header of the DL OFDMA PPDU and DL MU-MIMO PPDU,the following rules may be implemented. The Ack Policy of a QoS DATAMPDU in the A-MPDU may be set to Normal Ack or Implicit Block AckRequest. The sub-channel assignment information in the MAC header of allMPDUs in an A-MPDU may carry the same value. When the Ack Policy of aQoS DATA MPDU in the A-MPDU is set to No Ack, the sub-channel assignmentinformation is not carried in the DL OFDMA PPDU and DL MU-MIMO PPDU.

In an aspect, when the UL OFDMA is used for multiplexing the BA/ACKresponse to the DL OFDMA PPDU and DL MU-MIMO PPDU, the Block ACK Requestframe may be utilized as well by including the Block ACK Request in theDL OFDMA PPDU and DL MU-MIMO PPDU.

FIG. 42 illustrates an example of a Multi-User Block ACK Request(MU-BAR) frame. The MU-BAR frame may include a Frame Control field, aDuration/ID field, an RA field, a TA field, a BAR Control field,Per-User Block ACK Request field(s), and Per-User Sub-channel Assignmentfield(s). In an aspect, the MU-BAR frame may be utilized to solicitBA/ACKs from multiple STAs in UL MU transmissions. In an aspect, the BARControl field may include the number of users for requesting the BA/ACKresponse. To obtain a BA/ACK response from each user, the Per-User BlockRequest information and Per-User Sub-channel Assignment information(e.g., in the corresponding Per-User Block Request field and Per-UserSub-channel Assignment field) may be repeated in the MU-BAR frame.

The addressed recipient that receives the MU-BAR frame may return anAck/Block Ack frame that is carried in the UL OFDMA PPDU (e.g.,according to the sub-channel assignment information specified in thePer-User Sub-channel Assignment field of the MU-BAR frame).

In an aspect, one or more MU-BAR frames can be included in the DL OFDMAPPDU and DL MU-MIMO PPDU. Because a normal Block ACK Request frame maystill be used for requesting an Ack/Block Ack frame, the normal BlockACK Request frame may be carried in the SU PPDU. In an aspect, a normalBlock ACK Request may refer to an unmodified legacy Block ACK Request,and it solicits the Block ACK frame from the single receiver. In anaspect, the MU-BAR frame and the normal Block ACK Request frame shallnot be present together in the same PPDU. In other words, when thenormal Block ACK Request frame is present in the DL OFDMA PPDU and DLMU-MIMO PPDU, the MU-BAR frame shall not be present in the same PPDU.When the MU-BAR frame is present in the DL OFDMA and DL MU-MIMO PPDU,the normal Block ACK Request frame shall not be present in the samePPDU.

In an aspect, rather than use the MU-BAR frame of FIG. 42, a normalBlock ACK Request frame may be reused. In the DL OFDMA PPDU and DLMU-MIMO PPDU, at most one frame having the sub-channel assignmentinformation can be included in the A-MPDU. That frame shall be the firstor last MPDU in the A-MPDU. The Ack Policy of other QoS DATA MPDU in theA-MPDU shall be set to Block ACK because a Block ACK Request frame isalso present in the same A-MPDU. The BAR Ack Policy of the Block ACKRequest frame in the A-MPDU is not set to 0 (e.g., NormalAcknowledgement) and is set to a reserved value (e.g., 1—NoAcknowledgement). The Ack Policy behavior of receivers of the DL OFDMAand DL MU-MIMO PPDU may be differently interpreted according to thereception of the MPDU having the sub-channel assignment information inthe DL OFDMA PPDU and DL MU-MIMO PPDU.

For example, the BAR Ack Policy of the Block ACK Request frame in the DLOFDMA PPDU and DL MU-MIMO PPDU may be set to a reserved value forindicating the UL OFDMA-based ACK. If the reserved value is set to 1,the Ack Policy behavior of receivers of the DL OFDMA PPDU and DL MU-MIMOPPDU can be provided as follows.

BAR Ack Policy set to 01: [PSMP context] or [UL OFDMA context]

In a frame that is the power save multi-poll (PSMP) context:

-   -   i) When bit 6 of the Frame Control field is set to 1:    -   There may be a response frame to the frame that is received, but        it is neither the Ack frame nor any data frame of        subtype+CF-Ack. The Ack Policy sub-field for QoS CF-Poll and QoS        CF-Ack+CFPoll Data frames is set to this value.    -   ii) When bit 6 of the Frame Control field is set to 0:    -   The acknowledgement for a frame indicating PSMP Ack when it        appears in a PSMP downlink transmission time (PSMP-DTT) is to be        received in a later PSMP uplink transmission time (PSMP-UTT).        The acknowledgement for a frame indicating PSMP Ack when it        appears in a PSMP-UTT is to be received in a later PSMP-DTT.

In a frame that is the UL OFDMA context:

-   -   i) The addressed recipient that receives a frame having the        sub-channel assignment information returns an Ack/Block Ack        frame, either individually or as part of an A-MPDU starting a        SIFS after the PPDU carrying the frame, according to the        sub-channel assignment information specified in the received        frame.    -   ii) The addressed recipient that does not receive a frame having        the sub-channel assignment information takes no action upon the        receipt of the frame except for recording the state. The        recipient can expect a BlockAckReq frame in the future to which        it responds using the procedure described in a block        acknowledgement mechanism.

FIG. 43 illustrates an example of a frame having sub-channel assignmentinformation. The frame may include a Frame Control field, a Duration/IDfield, an RA field, a TA field, a Common Sub-channel Assignment Infofield, and Per-User Sub-channel Assignment Info 1 field through Per-UserSub-channel Assignment Info n field. One or more or no Per-UserSub-channel Assignment fields may be present between the Per-UserSub-channel Assignment Info 1 field and Per-User Sub-channel AssignmentInfo n field.

In an aspect, the Common Sub-channel Assignment Info field has thefollowing fields.

UL MU Duration (e.g., 9 bits) indicates a duration of a UL MUtransmission

Total LTFs (e.g., 3 bits) indicates the number of LTFs transmitted in aUL MU PPDU

LTF Duration (e.g., 1 bit) indicates an OFDMA symbol duration of an LTF

Guard Interval (e.g., 2 bits) indicates a guard interval of an LTF and aPSDU transmitted in a UL MU PPDU

STBC (e.g., 1 bit) indicates whether a STBC is applied for a UL MUtransmission

In an aspect, each Per-User Sub-channel Assignment Info field has thefollowing fields.

AID (e.g., 12 bits) indicates an association identifier (AID) of anuplink (UL) multi-user (MU) transmitter

RU Sub-Channel (e.g., 8 bits) indicates a frequency of a resource unit(RU) assigned for a UL MU transmission

RU MCS (e.g., 3 bits) indicates indicates a modulation coding scheme(MCS) of a UL MU transmission

RU STS (e.g., 3 bits) indicates the number of space-time streams of a ULMU transmission

RU Beamformed (e.g., 1 bit) indicates whether beamforming is applied fora UL MU transmission

RU Coding (e.g, 1 bit) indicates a coding type (BCC or LDPC) of a PSDUtransmitted in a UL MU PPDU

FIG. 44 illustrates an example of a structure (or numerology) of aresource unit (RU) distribution in an OFDMA transmission. In an aspect,FIG. 44 illustrates a numerology for an 80 MHz channel bandwidth. In anaspect, to support all possible RU combinations (e.g., 136 cases) for a160 MHz channel, the RU Sub-Channel sub-field may need 8 bits. In somecases, 8 bits of the RU Sub-Channel sub-field may have a nestedstructure. In an aspect, a nested structure of the RU Sub-Channelsub-field may help reduce signaling overhead.

FIG. 45 illustrates an example of a general framework of a nestedstructure of the RU Sub-Channel sub-field. The RU Sub-Channel sub-fieldmay include an Assigned RU Type sub-field, an Assigned RU Positionsub-field, and an Assigned RU Tone sub-field. In an aspect, the AssignedRU Type sub-field may specify the set of Assigned RUs. For example, theAssigned RU Type sub-field may be set to 0 for assigning 52 RU, 106 RU,and 242 RU. The Assigned RU Type sub-field may be set to 1 for assigning26 RU, 484 RU, and 996 RU. In an aspect, the Assigned RU Positionsub-field (e.g., 3 bits) may specify the frequency position of theassigned RU. In an aspect, the Assigned RU Tone sub-field (e.g., 3 bitsor 4 bits) may specify the number of tones of the assigned RU.

For example, when the Assigned RU Type sub-field is set to 0:

The Assigned RU Position sub-field (e.g., 3 bits) may be set to 000(e.g., RU is positioned on a first (lowest) 20 MHz), 001 (e.g., RU ispositioned on a second 20 MHz), 010 (e.g., RU is positioned on a third20 MHz), 011 (e.g., RU is positioned on a fourth 20 MHz), 100 (e.g., RUis positioned on a fifth 20 MHz), 101 (e.g., RU is positioned on a sixth20 MHz), 110 (e.g., RU is positioned on a seventh 20 MHz), and 111(e.g., RU is positioned on an eighth (highest) 20 MHz); and

The Assigned RU Tone sub-field (e.g., 3 bits) may be set to 000 (e.g.,assigned RU corresponds to a leftmost (first) 52-RU), 001 (e.g.,assigned RU corresponds to a second 52-RU), 010 (e.g., assigned RUcorresponds to a third 52-RU), 011 (e.g., assigned RU corresponds to afourth rightmost 52-RU), 100 (e.g., assigned RU corresponds to aleftmost (first) 106-RU), 101 (e.g., assigned RU corresponds to a secondrightmost 106-RU), 110 (e.g., assigned RU corresponds to 242-RU), and111 (Reserved).

For example, when the Assigned RU Type sub-field is set to 1:

The Assigned RU Position sub-field (e.g., 3 bits) may be set to 000(e.g., RU is positioned on a first (lowest) 20 MHz), 001 (e.g., RU ispositioned on a second 20 MHz), 010 (e.g., RU is positioned on a third20 MHz), 011 (e.g., RU is positioned on a fourth 20 MHz), 100 (e.g., RUis positioned on a fifth 20 MHz), 101 (e.g., RU is positioned on a sixth20 MHz), 110 (e.g., RU is positioned on a seventh 20 MHz), and 111(e.g., RU is positioned on a eighth (highest) 20 MHz);

The Assigned RU Tone sub-field (e.g., 4 bits) may be set to 0000 (e.g.,assigned RU corresponds to a leftmost (first) 26-RU), 0001 (e.g.,assigned RU corresponds to a second 26-RU), 0010 (e.g., assigned RUcorresponds to a third 26-RU), 0011 (e.g., assigned RU corresponds to afourth 26-RU), 0100 (e.g., assigned RU corresponds to a fifth 26-RU),0101 (e.g., assigned RU corresponds to a sixth 26-RU), 0110 (e.g.,assigned RU corresponds to a seventh 26-RU), 0111 (e.g., assigned RUcorresponds to an eighth 26-RU), 1000 (e.g., assigned RU corresponds toa rightmost (ninth) 26-RU), 1001 (e.g., assigned RU corresponds to acenter 26-RU), 1010 (e.g., assigned RU corresponds to a leftmost (first)484-RU), 1011 (e.g., assigned RU corresponds to a rightmost (second)484-RU), 1100 (e.g., assigned RU corresponds to 996-RU), 1101(Reserved), and 1111 (Reserved).

In an aspect, when the Assigned RU Type sub-field is set to 1, theAssigned RU Position sub-field may be set to 000 (e.g., corresponding RUis located on a first 80 MHz) or 111 (e.g., corresponding RU is locatedon a second 80 MHz) for center 26-RU, 484-RUs, and 996-RU.

In some cases, a DL MU PPDU may contain multiple frames havingsub-channel assignment information destined for different STAs. In thatcase, the RU Sub-Channel sub-field in the sub-channel assignmentinformation may be uniquely assigned to a single STA if a UL MU responsefrom the corresponding RU sub-channel is not designated for UL MU-MIMO.In an aspect, a same RU sub-channel in the multiple frames having thesub-channel assignment information can be assigned to different STAs ifa UL MU response from the corresponding RU sub-channel is designated forUL MU-MIMO.

In an aspect, a nested structure of the RU Sub-Channel sub-field mayhelp reduce signaling overhead. FIGS. 46A, 46B and 46C illustrate anexample of a sub-channel assignment method. More specifically, FIG. 46Aillustrates an example of a Common Sub-Channel Assignment Info field.FIGS. 46B and 46C illustrate examples of a Per-User Sub-ChannelAssignment Info field. In an aspect, a description of the varioussub-fields illustrated in FIGS. 46A, 46B, and 46C is the same as thatpreviously described.

In an aspect, in the Per-User Sub-channel Assignment Info field, the RUSub-Channel sub-field can be compressed when the Assigned RUs of eachuser are positioned on the same channel. For example, an assigned RU forSTA1 may be a first first (leftmost) 52-RU on a first lowest 20 MHz andan assigned RU for STA2 may be on a second 52-RU on a first lowest 20MHz. In that case, the RU Sub-Channel sub-fields in the Per-UserSub-channel Assignment Info field (e.g., indicating a frequency of aresource unit (RU) assigned for a UL MU transmission) may be encoded to0000000 and 0000001, respectively. In contrast, by using the nestedstructure of the RU Sub-Channel sub-field (e.g., shown in FIGS. 46B and46C), the Assigned RU Type sub-field (e.g., 0) and Assigned RU Positionsub-field (e.g., 000) may be commonly encoded for each user and adifferent part (e.g., the Assigned RU Tone sub-field, 000 for STA1 and001 for STA2) are separately encoded for each user.

In an aspect, a same RU sub-channel may be assigned to different STAsfor a UL MU-MIMO transmission. In the Per-User Sub-channel AssignmentInfo field, the RU Sub-Channel sub-field can be further compressed.These features are illustrated with reference to FIGS. 47A and 47B. Morespecifically, FIG. 47A illustrates an example of a Common Sub-ChannelAssignment Info field, and FIG. 47B illustrates an example of a Per-UserSub-Channel Assignment Info field. In an aspect, a description of thevarious sub-fields illustrated in FIGS. 47A and 47B is the same as thatpreviously described with reference to FIGS. 46A, 46B and 46C, but FIG.47B does not include an Assigned RU Tone field that is shown in FIGS.46B and 46C. As shown in FIG. 47B, the RU Sub-Channel sub-field may becommonly encoded, but the AID and other transmission parameter for a ULMU transmission may be separately encoded for each user.

In an aspect, a frame having sub-channel assignment information can beutilized for a frame having an HT Control field. FIG. 48 illustrates anexample of an HT Control field. In an aspect, sub-channel assignmentinformation may be encoded in the HT Control field. The HT Control fieldmay have a Control Type sub-field (e.g., 2 bits). The Control Typesub-field may be set to 00 when an intended behavior is a MCS FeedbackRequest (MRQ), set to 01 when an intended behavior is a MCS FeedbackResponse (MFB), and set to 10 when an intended behavior is a UL MUTrigger (UMT). Depending on a value contained in the Control Typesub-field, the HT Control field may have a different format. Forinstance, when the Control Type sub-field is set to 10, the HT Controlfield may consist of a Common Sub-channel Assignment Info field and aPer-User Sub-channel Assignment Info field. In an aspect, the detaileddescription of each sub-field is the same as with previous description.

In one or more aspects, a frame having sub-channel assignmentinformation may be aggregated with other MPDUs and transmitted to eachreceiver of the DL OFDMA PPDU and DL MU-MIMO PPDU. In an aspect, anexample of an A-MPDU format is provided by the table below.

Name of Context Definition of Context Data Enabled The A-MPDU istransmitted outside a PSMP sequence Immediate by a TXOP holder or an RDresponder or a UL MU Response responder including potential immediateresponses. Data Enabled The A-MPDU is transmitted outside a PSMPsequence No Immediate by a TXOP holder or a UL MU responder that doesnot Response include or solicit an immediate response. VHT single TheA-MPDU is transmitted within a VHT PPDU and MPDU context contains a VHTsingle MPDU. The trigger frame is present if it is transmitted by an AP.HE single The A-MPDU is transmitted within an HE PPDU and an MPDUcontext HE single MPDU with an optional trigger frame.

In an aspect, as shown in the table above, the frame having thesub-channel assignment information may be, or may be referred to as, atrigger frame. The trigger frame can be included in a Data EnabledImmediate Response, a Data Enabled No Immediate Response, a VHT singleMPDU context, and an HE single MPDU context.

In an aspect, A-MPDU contents in the HE single MPDU context are providedas follows.

MPDU Conditions Trigger frame At most one trigger is optionally presentif it is transmitted by an AP Any MPDU except An HE single MPDU for aTrigger frame

In an aspect, generally, the HE single MPDU may include any single MPDU.In such a case, in an aspect, a response to the HE single MPDU is not aUL MU PPDU. In some cases, to allow the use of a UL MU PPDU as aresponse to the HE single MPDU, the trigger frame can be included in theHE single MPDU. In an aspect, when a trigger frame is present in the HEsingle MPDU, the trigger frame should be the first MPDU in the A-MPDU.The HE single MPDU may be signaled by setting the EOF sub-field of theMPDU delimiter field of the first (and second) MPDU(s) in the A-MPDUto 1. The Ack Policy behavior of the HE single MPDU may be differentlyinterpreted according to the reception of the trigger frame.

In an aspect, when the addressed recipient receives the trigger frame,the address recipient may return a control response frame (e.g., if thecontrol response frame is needed) according to the sub-channelassignment information specified in the trigger frame. In an aspect,when the addressed recipient does not receive a trigger frame, theaddressed recipient takes no action upon the receipt of the A-MPDU. Inan aspect, the presence of the trigger frame in the HE single MPDU maybe signaled to the destination STA (e.g., an addressed recipient).

FIG. 49 illustrates an example of an A-MPDU format. In FIG. 49, a zerothbit B0 (denoted as EOF) may by utilized for providing an end of frame(EOF) indication. The EOF indication may be set to 1 in an A-MPDUsubframe that has 0 in the MPDU Length field and that is used to pad theA-MPDU in an HE PPDU. The EOF indication may be set to 1 in the MPDUdelimiter of an HE single MPDU. Otherwise, the EOF indication may be setto 0.

In this regard, the MPDU Length field may be utilized for indicating alength of the MPDU (e.g., in octets). The MPDU Length may be set to 0 ifno MPDU is present. In an aspect, an A-MPDU subframe with 0 in its MPDULength field may be used to meet the minimum MPDU start spacingrequirement and to pad the A-MPDU to fill the available space (e.g.,available octets) in an HE PPDU. In an aspect, a cylic redundancy check(CRC) field may include an 8-bit CRC of a preceding 16 bits. In anaspect, a Delimiter Signature field may include a pattern that may beused to detect an MPDU delimiter when scanning for an MPDU delimiter.

A first bit B1 (denoted as Control Response) in the A-MPDU delimiter maybe utilized for indicating a PPDU type of a control response frame. Inan aspect, when this bit is set to 0, the PPDU type of the controlresponse is SU. When this bit is set to 1, the PPDU type of the controlresponse is MU. The addressed recipient that receives the trigger framemay return a control response frame (e.g., if the control response frameis needed) according to the sub-channel assignment information specifiedin the trigger frame. In an aspect, when the addressed recipient doesnot receive the trigger frame, the addressed recipient takes no actionupon the receipt of the A-MPDU.

In some aspects, if the sub-channel assignment information can beimplicitly derived from the PHY RX parameter of the transmitted HEsingle MPDU, the trigger frame, which may be utilized for requesting aUL MU PPDU as a response of an HE single MPDU, may not be present in theHE single MPDU. Even in such a case, a signaling method may still beutilized (e.g., still be needed) for indicating a PPDU type of a controlresponse frame for an HE single MPDU.

In this regard, B1 (Control Response) in the A-MPDU delimiter may stillbe utilized to indicate a PPDU type of a control response frame with amodification of the receiver behavior compared with the previousdescription. As described above, when this bit is set to 0 or 1, thePPDU type of the control response is SU or MU, respectively. Theaddressed recipient may return a control response frame (e.g., if thecontrol response frame is needed) according to the sub-channelassignment information implicitly derived from the eliciting frame(e.g., rather than sub-channel assignment information specified in thetrigger frame).

FIG. 50 illustrates an example of a frame exchange sequence between anAP and multiple stations. In FIG. 50, a trigger frame can be included ina Control Response context. First, the AP may initiate a UL MU frameexchange sequence by transmitting a trigger frame. STA1 and STA2 mayeach transmit a respective UL MU PPDU in response to the trigger frame.After receiving the UL MU PPDUs from STA1 and STA2, the AP may transmita Multi-User Block ACK (MU-BAR) frame for acknowledging the UL MU PPDUsreceived from STA1 and STA2. In an aspect, for a follow-up UL MU frameexchange, a second trigger frame may be transmitted in an A-MPDU formatwith the MU-BAR frame.

In an aspect, to support the frame exchange sequence shown in FIG. 50, atrigger frame can be included in the Control Response context asfollows.

Name of Context Definition of Context Control The A-MPDU is transmittedby a STA that is neither a TXOP Response holder nor an RD responder or aUL MU initiator that also needs to transmit one of the followingimmediate response frames: Ack BlockAck frame with a TID for which anHT-immediate block ack agreement exists

In an aspect, A-MPDU contents in the Control Response context areprovided as follows.

MPDU Conditions Ack Ack frame transmitted in response One of these is toan MPDU that requires an Ack present at the start frame. of the A-MPDUBlockAck BlockAck frame with a TID that corresponds to an HT-immediateblock ack agreement. ActionNoAck +HTC Action No Ack frames carrying aManagement Action Body containing an explicit feedback response or BRPframe. Trigger frame At most one trigger is present if it is transmittedby an AP

In an aspect, when the AP initiates a UL MU frame exchange sequence bytransmitting a trigger frame, UL MU responders may have authority tochoose the A-MPDU contents carried in the UL MU response frame. In otherwords, in an aspect, if UL transmission time is allowed, any frames canbe included in the A-MPDU contents carried in the UL MU response frame.An example of A-MPDU contents is provided as follows.

Name of Context Definition of Context Data Enabled The A-MPDU istransmitted outside a PSMP sequence Immediate by a TXOP holder or an RDresponder or a UL MU Response responder including potential immediateresponses. Data Enabled The A-MPDU is transmitted outside a PSMPsequence No Immediate by a TXOP holder or a UL MU responder that doesnot Response include or solicit an immediate response. VHT single TheA-MPDU is transmitted within a VHT PPDU and MPDU context contains a VHTsingle MPDU. The trigger frame is present if it is transmitted by an AP.HE single The A-MPDU is transmitted within an HE PPDU and an MPDUcontext HE single MPDU with an optional trigger frame. Control TheA-MPDU is transmitted by a STA that is neither a Response TXOP holdernor an RD responder or a UL MU initiator that also needs to transmit oneof the following immediate response frames: Ack BlockAck frame with aTID for which an HT- immediate block ack agreement exists

In an aspect, when a UL MU responder has authority to choose the A-MPDUcontents carried in the UL MU response frame, UL MU scheduling at the APmay be affected by the A-MPDU contents. The A-MPDU contents may includea data frame, content frame, and/or management frame. For example, if aUL MU responder transmits a frame of a Data Enabled Immediate Responsecontext, the AP needs to assign one or more sub-channel(s) to theprevious UL MU responder in order to reply with the immediate response.In other words, a UL MU scheduling algorithm utilized on the AP side maybe affected by the A-MPDU contents carried in the UL MU response frame.In an aspect, the assigning of additional resources to the previous ULMU responder may increase the overhead for the UL MU transmission.

In an aspect, in order to address the effect of the UL MU schedulingalgorithm on the A-MPDU contents, a rule is provided as to whether aframe soliciting an immediate response can be included in the A-MPDUcontents carried in the UL MU response frame.

In one approach, when a UL MU response of a certain control frame typeis solicited by a trigger frame (e.g., Multi-User Block Ack Request orMulti-User Beamforming Report Poll frame), the corresponding UL MUresponder shall not include a frame soliciting an immediate response inthe A-MPDU contents carried in the UL MU response frame. In other words,if a STA receives the trigger frame for the Multi-User Block AckRequest, the UL MU response frame can include frames (e.g., Block Ackframe, Action No Ack management frame, DATA frame with the Ack Policyset to either No Ack or Block Ack) not soliciting an immediate responsein the A-MPDU contents carried in the UL MU response frame.

FIG. 51 illustrates an example of the approach described above withreference to a frame exchange sequence between an AP and multiplestations (e.g., STA1, STA2, STA3, and STA4). The AP may transmit adownlink (DL) multi-user PPDU to STA1, STA2, STA3, and STA4. STA1 andSTA2 may respond with a Block ACK frame in response to receiving thedownlink multi-user PPDU, but STA3 and STA4 do not respond with a frame(e.g., a Block ACK frame). In this example, the AP transmits a triggerframe including a Multi-User Block Ack Request (MU-BAR) frame. When STA3and STA4 receive the trigger frame for MU-BAR, STA3 and STA4 do not sendframes soliciting an immediate response in the A-MPDU contents carriedin the UL MU response frame. STA3 transmits only a Block ACK frame, andSTA4 transmits a frame having a Block ACK frame and a Data frame (e.g.,HE-DATA) with the Ack Policy set to either No Ack or Block Ack (e.g.,not set to implicit Block Ack Request).

In one or more aspects, a recipient (e.g., STA3, STA4) of a MU-BAR framecan transmit other data or management frame in addition to BA/ACK frameif it does not exceed the indicated UL MU duration.

It should be noted that the Data frame shown in FIG. 51 is not limitedto a data frame, and it can be one or more type(s) of frames (e.g., adata frame, a control frame, and/or a management frame). For example, arecipient (e.g., STA3, STA4) of a frame, such as a DL PPDU from an AP(e.g., a trigger frame having a MU-BAR frame), can generate and transmita UL PPDU as a response frame having at least one of a data frame, acontrol frame, or a management frame (or some combination thereof), inaddition to a BA or ACK frame, if the UL PPDU does not exceed theindicated UL MU duration (i.e., a duration of a UL MU transmission). Inone aspect, a UL MU duration may be a duration indicated (e.g.,scheduled or permitted) for a UL MU transmission. For the UL MUtransmission, the stations (e.g., STA3 and STA4) may transmit theirrespective UL PPDUs during the UL MU duration (e.g., as their immediateresponses to the frame from the AP). A DL PPDU from the AP (e.g., atrigger frame with a MU-BAR frame) may include information indicating aduration of the UL MU transmission. A UL MU duration does not exceed aTXOP limit. The Ack Policy for the data, control and/or managementframe(s) is not set to implicit Block Ack Request. The data, controland/or management frame(s) do not solicit an immediate response from theAP.

In another approach, the trigger frame may indicate whether a framesoliciting an immediate response can be included in the A-MPDU contentscarried in the UL MU response frame. For example, the trigger frame mayhave an A-MPDU contents type field set to 0 if the A-MPDU contentscarried in the UL MU response frame is Data Enabled Immediate Responsecontext, set to 1 if the A-MPDU contents carried in the UL MU responseframe is Data Enabled No Immediate Response context, set to 2 if theA-MPDU contents carried in the UL MU response frame is HE single MPDUcontext, and set to 3 if the A-MPDU contents carried in the UL MUresponse frame is Control Response context.

In an aspect, after receiving a Block ACK frame from the AP, the STA mayinclude a Block ACK Request frame in a following UL MU PPDU forrequesting an explicit acknowledgement information based on the BlockACK Request frame. The AP may receive a Block ACK Request from a UL MUPPDU and respond with a Block ACK frame whose Ack Policy is set to 1.Thus, the BA Control and BA Information fields (see, e.g., FIG. 35) arepresent in the Per-User ACK field of the Block ACK frame.

In an aspect, if AP correctly receives all MPDUs from the StartingSequence Number specified in the Starting Sequence Control field of theBlock ACK Request frame (e.g., sent by a STA of a UL MU PPDU amongmultiple UL MU PPDUs from multiple STAs), Ack Policy may be set to 0 forindicating the BA Control and BA Information fields are not present inthe Per-User ACK field.

In one or more aspects, when a STA transmits a UL MU PPDU, MPDUs havingmultiple TIDs can be aggregated in a single PSDU. If AP receives MPDUshaving multiple TIDs (e.g., TID1, TID2, etc.), a Block ACK frame isresponded with one of the following three frame formats described below.A format may be determined based on a category associated with an MPDUerror.

FIGS. 52 and 53 illustrate examples of a first frame format and itsassociated frame exchange sequence. In this regard, FIG. 52 illustratesan example of a Block ACK frame format. The Block ACK frame may includea frame control field, a duration/ID field, an RA field, a TA field,Per-User ACK fields, and an FCS field. In an aspect, each Per-User ACKfield may include an ACK Policy sub-field, an AID sub-field, and a TIDsub-field. In this regard, each Per-User ACK field may be, or may beconsidered as, a list of an ACK Policy information, AID information, andTID information. In an aspect, the Ack Policy sub-field, AID sub-field,and TID sub-field may be 1 bit, 11 bits, and 4 bits, respectively.

In an aspect, when the Ack Policy sub-field is set to a first value(e.g., 0), the BA Control and BA Information fields are not present inthe Per-User ACK field. This indicates an ACK of all MPDUs (e.g.,independent of TID) carried in the eliciting PPDU that was transmittedby the STA whose AID is indicated in the AID sub-field of Per-User ACKfield. In an aspect, the TID sub-field is set to a reserved value forindicating that all MPDUs, having different TIDs (e.g., two or moredifferent TIDs), are received by the AP. In an aspect, the reservedvalue is different from TID1, TID2, and any other TID associated withthe MPDUs. In an aspect, the reserved value is a predetermined value(e.g., 14). In another case in which all MPDUs have the same TID and allthe MPDUs are received by the AP, the Ack Policy sub-field may be set to0 and the TID set to the TID of all the MPDUs. In an aspect, when theAck Policy sub-field is set to a second value (e.g., 1), the BA Controland BA Information fields are present in the Per-User ACK field. In theforegoing, the first value and second value are 0 and 1, respectively,by way of non-limiting example. In other words, in some aspects, thefirst value may be 1 and the second value may be 0.

In an aspect, the BA Information sub-field includes a Block Ack StartingSequence Control sub-field and a Block Ack Bitmap sub-field. Thus, inthis aspect, when the Ack Policy sub-field is equal to the first value,the Block Ack Starting Sequence Control and Block Ack bitmap are notpresent in the Per-User ACK field, and when the Ack Policy sub-field isequal to the second value, the Block Ack Starting Sequence Control andBlock Ack bitmap are not present in the Per-User ACK field.

In an aspect, a Per-User ACK field may be referred to as a Per STA Infofield. In an aspect, the Ack Policy sub-field may be referred to as anAck Type sub-field. In an aspect, the Ack Policy sub-field, AIDsub-field, and TID sub-field form a Per AID TID Info sub-field. Thus, inthis aspect, the Per-User ACK field includes the Per AID TID Infosub-field.

FIG. 53 illustrates an example of a frame exchange sequence between anAP and multiple stations. In this example, the AP may request/elicit aUL MU PPDU from STA1 and STA2. The AP may transmit an uplink MU Pollframe to STA1 and STA2. STA1 may transmit a UL MU PPDU by aggregatingMPDUs having different TIDs (e.g., TID1 and TID2). The UL MU PPDUtransmitted by STA1 may include four MPDUs, denoted as MPDU1, MPDU2,MPDU3, and MPDU4, respectively, and each of these four MPDUs may have aseparate sequence number. For instance, in a case that the AP determines(e.g., based on a sequence number in the MPDUs), that MPDU1, MPDU3, andMPDU4 are successfully received by the AP, the AP may indicate in theacknowledgement bitmap that MPDU1, MPDU3, and MPDU4 are successfullyreceived and that MPDU2 was not received. In a case that all MPDUs(e.g., MPDU1, MPDU2, MPDU3, and MPDU4) are successfully received, theAck Policy sub-field may be set to 0 in the Block ACK frame. In anaspect, the Ack Policy sub-field being set to 0 is indicative of theBlock Ack Starting Sequence Control and Block Ack bitmap not beingpresent in the Per-User ACK field of the Block ACK frame. When the APreceives all MPDUs, in which the MPDUs may have one or more differentTIDs (e.g., TID1 and TID2), the AP may transmit a Block ACK frame (e.g.,containing an acknowledgement bitmap) of the format shown in FIG. 52.

FIGS. 54 and 55 illustrate examples of a second frame format and itsassociated frame exchange sequence. In this regard, FIG. 54 illustratesan example of a Block ACK frame format. In an aspect, each Per-User ACKfield includes concatenations of a list of an ACK Policy sub-field, anAID sub-field, a TID sub-field, a BA Control sub-field, and a BAInformation sub-field. In each list of the Per-User ACK field, when theAck Policy sub-field is set to 1, the BA Control and BA Informationfields are present for all TIDs from which at least one MPDU (e.g.,carried in the eliciting PPDU that was transmitted by the STA whose AIDis indicated in the AID sub-field of the Per-User ACK field) is notreceived by the AP. The TID sub-field may be set to a TID of MPDUs thatare acknowledged by the BA Control and BA Information fields in eachlist of the Per-User ACK field.

FIG. 55 illustrates an example of a frame exchange sequence between anAP and multiple stations. In this example, the AP may request/elicit aUL MU PPDU from STA1 and STA2. The AP may transmit an uplink MU Pollframe to STA1 and STA2. STA1 may transmit a UL MU PPDU by aggregatingMPDUs having different TIDs (e.g., TID1 and TID2) in FIG. 55. When theAP does not receive some or all of the MPDUs having TID1 and TID2, theAP may transmit a Block ACK frame of the format shown in FIG. 54.

FIGS. 56 and 57 illustrate examples of a third frame format and itsassociated frame exchange sequence. In this regard, FIG. 56 illustratesan example of a format of a Block ACK frame. In an aspect, each Per-UserACK field may include a combination of two lists. A first list includesan ACK Policy sub-field, an AID sub-field, and a TID sub-field. A secondlist includes an ACK Policy sub-field, an AID sub-field, a TIDsub-field, a BA Control sub-field, and a BA Information sub-field.

In the first list, since the Ack Policy sub-field is set to 0, the BAControl and BA Information fields are not present in that list for a TID(e.g., referred to as an ACK TID) from which all MPDUs (e.g., carried inthe eliciting PPDU that was transmitted by the STA whose AID isindicated in the AID sub-field of Per-User ACK field) are received bythe AP.

In the second list, since the Ack Policy sub-field is set to 1, the BAControl and BA Information fields are present in that for a TID (e.g.,referred to as BACK TID) from which at least one MPDU (e.g., carried inthe eliciting PPDU that was transmitted by the STA whose AID isindicated in the AID sub-field of Per-User ACK field) is not received byAP.

The TID sub-field may be set to an ACK TID if the TID sub-field ispresent in the first list and/or may be set to a BACK TID if the TIDsub-field is present in the second list.

FIG. 57 illustrates an example of a frame exchange sequence between anAP and multiple stations. In this example, the AP may request/elicit aUL MU PPDU from STA1 and STA2. The AP may transmit an uplink MU Pollframe to STA1 and STA2. STA1 may transmit a UL MU PPDU by aggregatingMPDUs having different TIDs (e.g., TID1 and TID2) in FIG. 57. When theAP receives all MPDUs having TID1 but the AP does not receive some MPDUshaving TID2, the AP may transmit a Block ACK frame of the format shownin FIG. 56. The first list is used for acknowledgement information ofMPDU having TID1, since all MPDUs having TID1 is received by the AP. Inthis case, TID1 corresponds to an ACK TID. The second list is used foracknowledgement information of MPDU having TID2, since at least someMPDUs having TID2 is not received by the AP. In this case, TID2corresponds to a BACK TID.

It should be noted that like reference numerals may designate likeelements. These components with the same reference numerals have certaincharacteristics that are the same, but as different figures illustratedifferent examples, the same reference numeral does not indicate that acomponent with the same reference numeral has the exact samecharacteristics. While the same reference numerals are used for certaincomponents, examples of differences with respect to a component aredescribed throughout this disclosure.

The embodiments provided herein have been described with reference to awireless LAN system; however, it should be understood that thesesolutions are also applicable to other network environments, such ascellular telecommunication networks, wired networks, etc.

An embodiment of the present disclosure may be an article of manufacturein which a non-transitory machine-readable medium (such asmicroelectronic memory) has stored thereon instructions which programone or more data processing components (generically referred to here asa “processor” or “processing unit”) to perform the operations describedherein. In other embodiments, some of these operations may be performedby specific hardware components that contain hardwired logic (e.g.,dedicated digital filter blocks and state machines). Those operationsmay alternatively be performed by any combination of programmed dataprocessing components and fixed hardwired circuit components.

In some cases, an embodiment of the present disclosure may be anapparatus (e.g., an AP STA, a non-AP STA, or another network orcomputing device) that includes one or more hardware and software logicstructure for performing one or more of the operations described herein.For example, as described above, the apparatus may include a memoryunit, which stores instructions that may be executed by a hardwareprocessor installed in the apparatus. The apparatus may also include oneor more other hardware or software elements, including a networkinterface, a display device, etc.

FIGS. 58A, 58B, 58C, 58D, and 58E illustrate flow charts of examples ofmethods for facilitating wireless communication. For explanatory andillustration purposes, the example processes 5810, 5820, 5830, 5840, and5850 may be performed by the wireless communication devices 111-115 ofFIG. 1 and their components such as a baseband processor 210, a MACprocessor 211, a MAC software processing unit 212, a MAC hardwareprocessing unit 213, a PHY processor 215, a transmitting signalprocessing unit 280 and/or a receiving signal processing unit 290;however, the example processes 5810, 5820, 5830, 5840, and 5850 are notlimited to the wireless communication devices 111-115 of FIG. 1 or theircomponents, and the example processes 5810, 5820, 5830, 5840, and 5850may be performed by some of the devices shown in FIG. 1, or otherdevices or components. Further for explanatory and illustrationpurposes, the blocks of the example processes 5810, 5820, 5830, 5840,and 5850 are described herein as occurring in serial or linearly.However, multiple blocks of the example processes 5810, 5820, 5830,5840, and 5850 may occur in parallel. In addition, the blocks of theexample processes 5810, 5820, 5830, 5840, and 5850 need not be performedin the order shown and/or one or more of the blocks/actions of theexample processes 5810, 5820, 5830, 5840, and 5850 need not beperformed.

Various examples of aspects of the disclosure are described below asclauses for convenience. These are provided as examples, and do notlimit the subject technology. As an example, some of the clausesdescribed below are illustrated in FIGS. 58A, 58B, 58C, 58D, and 58E.

Clause A. A station for facilitating communication in a wireless networkfor a multi-user transmission, the access point comprising: one or morememories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: generating afirst frame for the station, wherein the first frame comprises aplurality of media access control protocol data units (MPDUs), andwherein each of the plurality of MPDUs is associated with a trafficidentifier (TID); transmitting the first frame to an access point; andreceiving a second frame comprising an indication that all of theplurality of MPDUs having TIDs are received.

Clause B. An access point for facilitating communication in a wirelessnetwork for a multi-user transmission, the access point comprising: oneor more memories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: receiving afirst frame from a station, wherein the first frame comprises aplurality of media access control protocol data units (MPDUs), and eachof the plurality of MPDUs is associated with a traffic identifier (TID);generating a second frame based on the first frame, wherein the secondframe comprises an indication that all of the plurality of MPDUs havingTIDs are received; and transmitting the second frame to the station.

Clause C. A computer-implemented method of facilitating communication ina wireless network for a multi-user transmission, thecomputer-implemented method comprising: generating a first frame,wherein the first frame comprises a plurality of media access controlprotocol data units (MPDUs), and wherein each of the plurality of MPDUsis associated with a traffic identifier (TID); transmitting the firstframe to an access point; and receiving a second frame, wherein thesecond frame indicates that all of the plurality of MPDUs having TIDsare received.

Clause D. A station for facilitating communication in a wireless networkfor a multi-user transmission, the station comprising: one or morememories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: receiving afirst frame from an access point; generating a second frame in responseto the received first frame, wherein the second frame comprises anacknowledgement frame and at least one additional frame when the secondframe, with the at least one additional frame, does not exceed aduration of the multi-user transmission; and transmitting, to the accesspoint, the second frame during the duration of the multi-usertransmission.

Clause E. An access point for facilitating communication in a wirelessnetwork for multi-user transmission, the access point comprising: one ormore memories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: transmitting afirst frame to a first plurality of stations; receiving a second framefrom at least a first station of the first plurality of stations inresponse to the first frame; and determining that the second framecomprises an acknowledgement frame and at least one additional frame,wherein an acknowledgement policy of the at least one additional frameis not set to elicit an immediate response to the second frame.

Each of the implementations of Clauses D and E may include one or moreof the following additional clauses in any combination, may include someportions of one or more of the following additional clauses in anycombination, and/or may include some combination of any of theforegoing.

Clause 1: wherein the first frame is a multi-user block acknowledgementrequest (MU BAR) frame associated with a plurality of stations, theplurality of stations comprising the station.

Clause 2: wherein the at least one additional frame comprises at leastone of a data frame or a management frame.

Clause 3: wherein the at least one additional frame comprises at leastone of a data frame, a management frame, or a control frame.

Clause 4: wherein an acknowledgement policy of the at least oneadditional frame is not set to an implicit block acknowledgementrequest.

Clause 5: wherein the acknowledgement frame is a block acknowledgement(BA) frame.

Clause 6: wherein the first frame comprises information indicating theduration of the multi-user transmission.

Clause 7: wherein the first frame is a multi-user block acknowledgementrequest (MU BAR) frame.

Clause 8: wherein the at least one additional frame comprises at leastone of a data frame, a management frame, or a control frame.

Clause 9: wherein the one or more processors are further configured tocause:

prior to transmitting the first frame, transmitting a third frame to asecond plurality of stations, wherein the second plurality of stationscomprises the first plurality of stations;

determining that in response to the third frame, no response frame isreceived from any of the first plurality of stations; and

generating the first frame in response to the determining that noresponse frame is received.

Clause 10: wherein the one or more processors are further configured tocause receiving a third frame from a second station of the firstplurality of stations in response to the first frame, wherein the thirdframe comprises a single media access control protocol data unit (MPDU),which consists of a block acknowledgement (BA) frame.

In one or more aspects, additional clauses are described below.

A method comprising one or more methods or operations described herein.

An apparatus or a station comprising one or more memories (e.g., 240,one or more internal, external or remote memories, or one or moreregisters) and one or more processors (e.g., 210) coupled to the one ormore memories, the one or more processors configured to cause theapparatus to perform one or more methods or operations described herein.

An apparatus or a station comprising one or more memories (e.g., 240,one or more internal, external or remote memories, or one or moreregisters) and one or more processors (e.g., 210 or one or moreportions), wherein the one or more memories store instructions that,when executed by the one or more processors, cause the one or moreprocessors to perform one or more methods or operations describedherein.

An apparatus or a station comprising means (e.g., 210) adapted forperforming one or more methods or operations described herein.

A computer-readable storage medium (e.g., 240, one or more internal,external or remote memories, or one or more registers) comprisinginstructions stored therein, the instructions comprising code forperforming one or more methods or operations described herein.

A computer-readable storage medium (e.g., 240, one or more internal,external or remote memories, or one or more registers) storinginstructions that, when executed by one or more processors (e.g., 210 orone or more portions), cause the one or more processors to perform oneor more methods or operations described herein.

In one aspect, a method may be an operation, an instruction, or afunction and vice versa. In one aspect, a clause may be amended toinclude some or all of the words (e.g., instructions, operations,functions, or components) recited in other one or more clauses, one ormore sentences, one or more phrases, one or more paragraphs, and/or oneor more claims.

To illustrate the interchangeability of hardware and software, itemssuch as the various illustrative blocks, modules, components, methods,operations, instructions, and algorithms have been described generallyin terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.Skilled artisans may implement the described functionality in varyingways for each particular application.

A reference to an element in the singular is not intended to mean oneand only one unless specifically so stated, but rather one or more. Forexample, “a” module may refer to one or more modules. An elementproceeded by “a,” “an,” “the,” or “said” does not, without furtherconstraints, preclude the existence of additional same elements.

Headings and subheadings, if any, are used for convenience only and donot limit the invention. The word exemplary is used to mean serving asan example or illustration. To the extent that the term include, have,or the like is used, such term is intended to be inclusive in a mannersimilar to the term comprise as comprise is interpreted when employed asa transitional word in a claim. Relational terms such as first andsecond and the like may be used to distinguish one entity or action fromanother without necessarily requiring or implying any actual suchrelationship or order between such entities or actions.

Phrases such as an aspect, the aspect, another aspect, some aspects, oneor more aspects, an implementation, the implementation, anotherimplementation, some implementations, one or more implementations, anembodiment, the embodiment, another embodiment, some embodiments, one ormore embodiments, a configuration, the configuration, anotherconfiguration, some configurations, one or more configurations, thesubject technology, the disclosure, the present disclosure, othervariations thereof and alike are for convenience and do not imply that adisclosure relating to such phrase(s) is essential to the subjecttechnology or that such disclosure applies to all configurations of thesubject technology. A disclosure relating to such phrase(s) may apply toall configurations, or one or more configurations. A disclosure relatingto such phrase(s) may provide one or more examples. A phrase such as anaspect or some aspects may refer to one or more aspects and vice versa,and this applies similarly to other foregoing phrases.

A phrase “at least one of” preceding a series of items, with the terms“and” or “or” to separate any of the items, modifies the list as awhole, rather than each member of the list. The phrase “at least one of”does not require selection of at least one item; rather, the phraseallows a meaning that includes at least one of any one of the items,and/or at least one of any combination of the items, and/or at least oneof each of the items. By way of example, each of the phrases “at leastone of A, B, and C” or “at least one of A, B, or C” refers to only A,only B, or only C; any combination of A, B, and C; and/or at least oneof each of A, B, and C.

It is understood that the specific order or hierarchy of steps,operations, or processes disclosed is an illustration of exemplaryapproaches. Unless explicitly stated otherwise, it is understood thatthe specific order or hierarchy of steps, operations, or processes maybe performed in different order. Some of the steps, operations, orprocesses may be performed simultaneously. The accompanying methodclaims, if any, present elements of the various steps, operations orprocesses in a sample order, and are not meant to be limited to thespecific order or hierarchy presented. These may be performed in serial,linearly, in parallel or in different order. It should be understoodthat the described instructions, operations, and systems can generallybe integrated together in a single software/hardware product or packagedinto multiple software/hardware products.

The disclosure is provided to enable any person skilled in the art topractice the various aspects described herein. In some instances,well-known structures and components are shown in block diagram form inorder to avoid obscuring the concepts of the subject technology. Thedisclosure provides various examples of the subject technology, and thesubject technology is not limited to these examples. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the principles described herein may be applied to otheraspects.

All structural and functional equivalents to the elements of the variousaspects described throughout the disclosure that are known or later cometo be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. § 112, sixth paragraph, unless theelement is expressly recited using a phrase means for or, in the case ofa method claim, the element is recited using the phrase step for.

The title, background, brief description of the drawings, abstract, anddrawings are hereby incorporated into the disclosure and are provided asillustrative examples of the disclosure, not as restrictivedescriptions. It is submitted with the understanding that they will notbe used to limit the scope or meaning of the claims. In addition, in thedetailed description, it can be seen that the description providesillustrative examples and the various features are grouped together invarious implementations for the purpose of streamlining the disclosure.The method of disclosure is not to be interpreted as reflecting anintention that the claimed subject matter requires more features thanare expressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed configuration or operation. The following claims arehereby incorporated into the detailed description, with each claimstanding on its own as a separately claimed subject matter.

The claims are not intended to be limited to the aspects describedherein, but are to be accorded the full scope consistent with thelanguage claims and to encompass all legal equivalents. Notwithstanding,none of the claims are intended to embrace subject matter that fails tosatisfy the requirements of the applicable patent law, nor should theybe interpreted in such a way.

What is claimed is:
 1. A station for facilitating communication in awireless network for a multi-user transmission, the station comprising:one or more memories; and one or more processors coupled to the one ormore memories, the one or more processors configured to cause:generating a first frame that comprises a plurality of data units, andwherein each of the plurality of data units includes trafficinformation; transmitting the first frame to an access point; andreceiving a second frame comprising a plurality of per stationinformation fields, each of the plurality of per station informationfields comprising a predetermined value.
 2. The station of claim 1,wherein the traffic information includes a traffic identifier (TID)associated with a respective one of the plurality of data units.
 3. Thestation of claim 2, wherein the second frame comprises an indicationthat all of the plurality of data units having TIDs are received, andwherein the indication corresponds to one of a plurality ofpredetermined values in the plurality of per station information fields.4. The station of claim 3, wherein each of the plurality of per stationinformation fields comprises a TID field, and wherein the TID field isset to the predetermined value to provide the indication.
 5. The stationof claim 2, wherein a TID of one of the plurality of data units isdifferent from a TID of another one of the plurality of data units. 6.The station of claim 1, wherein each of a plurality of predeterminedvalues in the plurality of per station information fields is differentfrom values of the traffic information.
 7. The station of claim 1,wherein each of the plurality of per station information fieldscomprises an acknowledgement type (ACK Type) field, and wherein, whenthe ACK Type field is set to the predetermined value, the second frameexcludes a block acknowledgement (Block Ack) starting sequence controland a Block Ack bitmap.
 8. The station of claim 1, wherein each of theplurality of per station information fields comprises an acknowledgementtype (ACK Type) field and a TID field, wherein the ACK Type field is setto a first predetermined value and the TID field is set to a secondpredetermined value.
 9. The station of claim 1, wherein the first framecomprises a block acknowledgement request (BAR) frame, and wherein thesecond frame comprises a block acknowledgement (BA) frame.
 10. Thestation of claim 1, wherein the first frame contains at least a sequencenumber to enable the access point to determine whether each of theplurality of data units is received by the access point.
 11. An accesspoint for facilitating communication in a wireless network for amulti-user transmission, the access point comprising: one or morememories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: receiving afirst frame from a station, wherein the first frame comprises aplurality of data units, and wherein each of the plurality of data unitsincludes traffic information; generating a second frame based on thefirst frame, wherein the second frame comprises a plurality of perstation information fields, each of the plurality of per stationinformation fields comprising a predetermined value; and transmittingthe second frame to the station.
 12. The access point of claim 11,wherein the traffic information includes a traffic identifier (TID)associated with a respective one of the plurality of data units.
 13. Theaccess point of claim 12, wherein the second frame comprises anindication that all of the plurality of data units having TIDs arereceived, wherein the indication corresponds to one of a plurality ofpredetermined values in the plurality of per station information fields.14. The access point of claim 13, wherein each of the plurality of perstation information fields comprises a TID field, and wherein the TIDfield is set to the predetermined value to provide the indication. 15.The access point of claim 12, wherein each of the plurality of perstation information fields comprises an acknowledgement type (ACK Type)field and a TID field, wherein the ACK Type field is set to a firstpredetermined value and the TID field is set to a second predeterminedvalue.
 16. A computer-implemented method of facilitating communicationin a wireless network for a multi-user transmission, thecomputer-implemented method comprising: generating a first frame thatcomprises a plurality of data units, and wherein each of the pluralityof data units includes traffic information; transmitting the first frameto an access point; and receiving a second frame comprising a pluralityof per station information fields, each of the plurality of per stationinformation fields comprising a predetermined value.
 17. Thecomputer-implemented method of claim 16, wherein the traffic informationincludes a traffic identifier (TID) associated with a respective one ofthe plurality of data units, wherein the second frame comprises anindication that all of the plurality of data units having TIDs arereceived, wherein the indication corresponds to one of a plurality ofpredetermined values in the plurality of per station information fields,wherein each of the plurality of per station information fieldscomprises a TID field, and wherein the TID field is set to thepredetermined value to provide the indication.
 18. Thecomputer-implemented method of claim 17, wherein a TID of one of theplurality of data units is different from a TID of another one of theplurality of data units.
 19. The computer-implemented method of claim16, wherein each of the plurality of per station information fieldscomprises an acknowledgement type (ACK Type) field, and wherein, whenthe ACK Type field is set to the predetermined value, the second frameexcludes a block acknowledgement (Block Ack) starting sequence controland a Block Ack bitmap.
 20. The computer-implemented method of claim 16,wherein each of the plurality of per station information fieldscomprises an acknowledgement type (ACK Type) field and a TID field,wherein the ACK Type field is set to a first predetermined value and theTID field is set to a second predetermined value.